diff --git a/jscomp/bin/all_ounit_tests.ml b/jscomp/bin/all_ounit_tests.ml
index 84362790af..6a8fcda6a7 100644
--- a/jscomp/bin/all_ounit_tests.ml
+++ b/jscomp/bin/all_ounit_tests.ml
@@ -3529,6 +3529,7 @@ val js_array_ctor : string
 val js_type_number : string
 val js_type_string : string
 val js_type_object : string
+val js_type_boolean : string
 val js_undefined : string
 val js_prop_length : string
 
@@ -3663,6 +3664,7 @@ let js_array_ctor = "Array"
 let js_type_number = "number"
 let js_type_string = "string"
 let js_type_object = "object" 
+let js_type_boolean = "boolean"
 let js_undefined = "undefined"
 let js_prop_length = "length"
 
@@ -6895,9 +6897,9 @@ val make_unused : unit -> Ident.t
 val convert : string -> string
 
 
-val undefined : Ident.t 
+
 val is_js_or_global : Ident.t -> bool
- val nil : Ident.t 
+
 
 
 val compare : Ident.t -> Ident.t -> int
@@ -7219,9 +7221,6 @@ let reset () =
   String_hashtbl.clear js_module_table
 
 
-let undefined = create_js "undefined"
-let nil = create_js "null"
-
 (* Has to be total order, [x < y]
    and [x > y] should be consistent
    flags are not relevant here
diff --git a/jscomp/core/bs_conditional_initial.ml b/jscomp/core/bs_conditional_initial.ml
index 9b0bf7299b..df5ba896e9 100644
--- a/jscomp/core/bs_conditional_initial.ml
+++ b/jscomp/core/bs_conditional_initial.ml
@@ -25,7 +25,7 @@
 
 let setup_env () =
 #if BS_DEBUG then
-    Js_config.set_debug_file "pipe_syntax.ml";
+    Js_config.set_debug_file "gpr_2700_test.ml";
 #end
   Lexer.replace_directive_bool "BS" true;
   Lexer.replace_directive_string "BS_VERSION"  Bs_version.version
diff --git a/jscomp/core/j.ml b/jscomp/core/j.ml
index af5bebecfd..b580e3b5e1 100644
--- a/jscomp/core/j.ml
+++ b/jscomp/core/j.ml
@@ -102,68 +102,17 @@ and expression_desc =
   | Length of expression * length_object
   | Char_of_int of expression
   | Char_to_int of expression 
-  | Is_null_undefined_to_boolean of expression 
+  | Is_null_or_undefined of expression 
     (** where we use a trick [== null ] *)
-  | Array_of_size of expression 
-    (* used in [#create_array] primitive, note having
-       uninitilized array is not as bad as in ocaml, 
-       since GC does not rely on it
-     *)
   | Array_copy of expression (* shallow copy, like [x.slice] *)
-  | Array_append of expression * expression (* For [caml_array_append]*)
-  (* | Tag_ml_obj of expression *)
-  | String_append of expression * expression 
 
-  | Anything_to_number of expression
+  | String_append of expression * expression 
   | Bool of bool (* js true/false*)
   (* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence 
      [typeof] is an operator     
   *)
   | Typeof of expression
   | Js_not of expression (* !v *)
-  | String_of_small_int_array of expression 
-    (* String.fromCharCode.apply(null, args) *)
-    (* Convert JS boolean into OCaml boolean 
-       like [+true], note this ast talks using js
-       terminnology unless explicity stated                       
-     *)
-  | Json_stringify of expression 
-  (* TODO: in the future, it might make sense to group primitivie by type,
-     which makes optimizations easier
-     {[ JSON.stringify(value, replacer[, space]) ]}
-  *)
-  | Anything_to_string of expression
-  (* for debugging utitlites, 
-     TODO:  [Dump] is not necessary with this primitive 
-     Note that the semantics is slightly different from [JSON.stringify]     
-     {[
-       JSON.stringify("x")       
-     ]}
-     {[
-       ""x""       
-     ]}     
-     {[
-       JSON.stringify(undefined)       
-     ]}     
-     {[
-       undefined       
-     ]}
-     {[ '' + undefined
-     ]}     
-     {[ 'undefined'
-     ]}     
-  *)      
-  | Dump of Js_op.level * expression list
-  (* TODO: 
-     add 
-     {[ Assert of bool * expression ]}     
-  *)              
-    (* to support 
-       val log1 : 'a -> unit
-       val log2 : 'a -> 'b -> unit 
-       val log3 : 'a -> 'b -> 'c -> unit 
-     *)
-
   (* TODO: Add some primitives so that [js inliner] can do a better job *)  
   | Seq of expression * expression
   | Cond of expression * expression * expression
@@ -178,11 +127,6 @@ and expression_desc =
        if it's know at compile time, we can turn it into
        f(args[0], args[1], ... )
      *)
-  | Bind of expression * expression
-  (* {[ Bind (a,b) ]}
-     is literally
-     {[ a.bind(b) ]}
-  *)
   | Call of expression * expression list * Js_call_info.t
     (* Analysze over J expression is hard since, 
         some primitive  call is translated 
@@ -250,7 +194,8 @@ and expression_desc =
   *)      
   | Number of number
   | Object of property_map
-
+  | Undefined 
+  | Null
 and for_ident_expression = expression (* pure*)
 
 and finish_ident_expression = expression (* pure *)
diff --git a/jscomp/core/js_analyzer.ml b/jscomp/core/js_analyzer.ml
index 0ac91704fd..949c132abd 100644
--- a/jscomp/core/js_analyzer.ml
+++ b/jscomp/core/js_analyzer.ml
@@ -83,13 +83,15 @@ let free_variables_of_expression used_idents defined_idents st =
 
 let rec no_side_effect_expression_desc (x : J.expression_desc)  = 
   match x with 
+  | Undefined
+  | Null
   | Bool _ 
   | Var _ 
   | Unicode _ -> true 
   | Fun _ -> true
   | Number _ -> true (* Can be refined later *)
   | Access (a,b) -> no_side_effect a && no_side_effect b 
-  | Is_null_undefined_to_boolean b -> no_side_effect b 
+  | Is_null_or_undefined b -> no_side_effect b 
   | Str (b,_) -> b    
   | Array (xs,_mutable_flag)  
   | Caml_block (xs, _mutable_flag, _, _)
@@ -100,10 +102,8 @@ let rec no_side_effect_expression_desc (x : J.expression_desc)  =
         the block is mutable does not mean this operation is non-pure
     *)
     List.for_all no_side_effect  xs 
-  | Bind(fn, obj) -> no_side_effect fn && no_side_effect obj
   | Object kvs -> 
     List.for_all (fun (_property_name, y) -> no_side_effect y ) kvs 
-  | Array_append (a,b) 
   | String_append (a,b)
   | Seq (a,b) -> no_side_effect a && no_side_effect b 
   | Length (e, _)
@@ -115,15 +115,8 @@ let rec no_side_effect_expression_desc (x : J.expression_desc)  =
   | Bin (op, a, b) -> 
     op <> Eq && no_side_effect a && no_side_effect b     
   | Math _ 
-  | Array_of_size _
   | Array_copy _ 
-  (* | Tag_ml_obj _ *)
-  | J.Anything_to_number _
   | Js_not _
-  | String_of_small_int_array _ 
-  | Json_stringify _ 
-  | Anything_to_string _ 
-  | Dump _ 
   | Cond _ 
 
   | FlatCall _ 
@@ -184,6 +177,8 @@ let rec eq_expression
     ({expression_desc = x0}  : J.expression) 
     ({expression_desc = y0}  : J.expression) = 
   begin match x0  with 
+    | Null -> y0 = Null
+    | Undefined -> y0 = Undefined
     | Number (Int i) -> 
       begin match y0 with  
         | Number (Int j)   -> i = j 
@@ -244,12 +239,6 @@ let rec eq_expression
           p0 = p1 && b0 =  b1 && eq_expression e0 e1
         |  _ -> false 
       end
-    | Dump (l0,es0) -> 
-      begin match y0 with 
-        | Dump(l1,es1) -> 
-          l0 = l1 && eq_expression_list es0 es1
-        | _ -> false     
-      end
     | Seq (a0,b0) -> 
       begin match y0 with       
         | Seq(a1,b1) -> 
@@ -264,23 +253,13 @@ let rec eq_expression
     | Length _ 
     | Char_of_int _
     | Char_to_int _ 
-    | Is_null_undefined_to_boolean _ 
-    | Array_of_size _
+    | Is_null_or_undefined _ 
     | Array_copy _ 
-    | Array_append _ 
     | String_append _ 
-    | Anything_to_number _ 
-
     | Typeof _ 
     | Js_not _ 
-    | String_of_small_int_array _ 
-    | Json_stringify _ 
-    | Anything_to_string _ 
-
-
     | Cond _ 
     | FlatCall  _
-    | Bind _ 
     | String_access _ 
 
     | New _ 
diff --git a/jscomp/core/js_dump.ml b/jscomp/core/js_dump.ml
index d73b48f037..959b40ee9c 100644
--- a/jscomp/core/js_dump.ml
+++ b/jscomp/core/js_dump.ml
@@ -421,6 +421,11 @@ and expression l cxt  f (exp : J.expression) : Ext_pp_scope.t =
 and
   expression_desc cxt (l:int) f x : Ext_pp_scope.t  =
   match x with
+  | Null ->
+    P.string f L.null; cxt 
+  | Undefined 
+    -> 
+    P.string f L.undefined; cxt 
   | Var v ->
     vident cxt f v
   | Bool b ->
@@ -476,16 +481,7 @@ and
     in
     if l > 15 then P.paren_group f 1 action
     else action ()
-  | Bind (a,b) ->
-    (* a.bind(b)
-       {[ fun b -> a.bind(b) ==? a.bind ]}
-    *)
-    begin
-      expression_desc cxt l f
-        (Call ({expression_desc = Dot(a,L.bind, true); comment = None }, [b],
-               {arity = Full; call_info = Call_na}))
-    end
-
+  
   | FlatCall(e,el) ->
     P.group f 1 (fun _ ->
         let cxt = expression 15 cxt f e in
@@ -498,34 +494,6 @@ and
             expression 1 cxt f el
           )
       )
-  | String_of_small_int_array ({expression_desc = desc } as e) ->
-    let action () =
-      P.group f 1 (fun _ ->
-          P.string f L.string_cap;
-          P.string f L.dot ;
-          P.string f L.fromCharcode;
-          begin match desc with
-            | Array (el, _mutable)
-              ->
-              P.paren_group f 1 (fun _ -> arguments cxt f el)
-            | _ ->
-              P.string f L.dot ;
-              P.string f L.apply;
-              P.paren_group f 1 (fun _ ->
-                  P.string f L.null;
-                  P.string f L.comma;
-                  expression 1 cxt  f e  )
-          end )
-    in
-    if l > 15 then P.paren_group f 1 action
-    else action ()
-
-
-  | Array_append (e, el) ->
-    P.group f 1 (fun _ ->
-        let cxt = expression 15 cxt f e in
-        P.string f ".concat";
-        P.paren_group f 1 (fun _ -> arguments cxt f [el]))
 
   | Array_copy e ->
     P.group f 1 (fun _ ->
@@ -534,27 +502,6 @@ and
         P.string f "()" ;
         cxt
       )
-
-  | Dump (level, el) ->
-    let obj =
-      match level with
-      | Log -> "log"
-      | Info -> "info"
-      | Warn -> "warn"
-      | Error -> "error" in
-    P.group f 1 (fun _ ->
-        P.string f L.console;
-        P.string f L.dot;
-        P.string f obj ;
-        P.paren_group f 1 (fun _ -> arguments cxt f el))
-  | Json_stringify e
-    ->
-    P.group f 1 (fun _ ->
-        P.string f L.json ;
-        P.string f L.dot;
-        P.string f L.stringify;
-        P.paren_group f 1 (fun _ -> expression 0 cxt f e )
-      )
   | Char_to_int e ->
     begin match e.expression_desc with
       | String_access (a,b) ->
@@ -640,20 +587,7 @@ and
       else action ()
     );
     cxt
-  | J.Anything_to_number e
-    ->
-    let action () =
-      P.group f 0 @@ fun _ ->
-      P.string f "+" ;
-      expression 13 cxt f e
-    in
-    (* need to tweak precedence carefully
-       here [++x --> +(+x)]
-    *)
-    if l > 12
-    then P.paren_group f 1 action
-    else action ()
-  | Is_null_undefined_to_boolean e ->
+  | Is_null_or_undefined e ->
     let action = (fun _ ->
         let cxt = expression 1 cxt f e in
         P.space f ;
@@ -791,11 +725,6 @@ and
         P.space f ;
         expression 13 cxt  f delta
     end
-  | Anything_to_string e ->
-    (* Note that we should not apply any smart construtor here,
-       it's purely  a convenice for pretty-printing
-    *)
-    expression_desc cxt l f (Bin (Plus, E.empty_string_literal , e))
 
   | Bin (Minus, {expression_desc = Number (Int {i=0l;_} | Float {f = "0."})}, e)
     (* TODO:
@@ -929,16 +858,6 @@ and
     in
     if l > 15 then P.paren_group f 1 action else action ()
 
-  | Array_of_size e ->
-    let action () =
-      P.group f 1 @@ fun _ ->
-      P.string f L.new_;
-      P.space f;
-      P.string f L.array;
-      P.paren_group f 1 @@ fun _ -> expression 0 cxt f e
-    in
-    if l > 15 then P.paren_group f 1 action else action ()
-
   | Cond (e, e1, e2) ->
     let action () =
       (* P.group f 1 @@ fun _ ->  *)
@@ -1119,39 +1038,33 @@ and statement_desc top cxt f (s : J.statement_desc) : Ext_pp_scope.t =
       | Caml_block_set_tag _
       | Length _
       | Caml_block_set_length _
-      | Anything_to_string _
-      | String_of_small_int_array _
       | Call _
-      | Array_append _
       | Array_copy _
       | Caml_block_tag _
       | Seq _
       | Dot _
       | Cond _
       | Bin _
-      | Is_null_undefined_to_boolean _
+      | Is_null_or_undefined _
       | String_access _
       | Access _
-      | Array_of_size _
       | String_append _
       | Char_of_int _
       | Char_to_int _
-      | Dump _
-      | Json_stringify _
       | Math _
       | Var _
+      | Undefined
+      | Null
       | Str _
       | Unicode _
       | Array _
       | Caml_block  _
       | FlatCall _
       | Typeof _
-      | Bind _
       | Number _
       | Js_not _
       | Bool _
       | New _
-      | J.Anything_to_number _
         -> false
       (* e = function(x){...}(x);  is good
       *)
diff --git a/jscomp/core/js_dump_lit.ml b/jscomp/core/js_dump_lit.ml
index 8d8d473a72..74da7ce126 100644
--- a/jscomp/core/js_dump_lit.ml
+++ b/jscomp/core/js_dump_lit.ml
@@ -73,6 +73,7 @@ let bind = "bind"
 let math = "Math"
 let apply = "apply"
 let null = "null"
+let undefined = "undefined"
 let string_cap = "String"
 let fromCharcode = "fromCharCode"
 let eq = "="
diff --git a/jscomp/core/js_exp_make.ml b/jscomp/core/js_exp_make.ml
index 0a4de5223a..55adc03e8f 100644
--- a/jscomp/core/js_exp_make.ml
+++ b/jscomp/core/js_exp_make.ml
@@ -87,10 +87,11 @@ let var ?comment  id  : t =
 let js_global ?comment  (v : string) =
   var ?comment (Ext_ident.create_js v )
   
-let undefined  = var Ext_ident.undefined
-
-let nil = var Ext_ident.nil  
+let undefined  : t = 
+    {expression_desc = Undefined ; comment = None}
 
+let nil : t = 
+    {expression_desc = Null ; comment = None}
 let call ?comment ~info e0 args : t = 
   {expression_desc = Call(e0,args,info); comment }
 
@@ -173,14 +174,6 @@ let make_block ?comment tag tag_info es mutable_flag : t =
     comment 
   }    
 
-(* let uninitialized_object ?comment tag size : t = 
-  { expression_desc = Caml_uninitialized_obj(tag,size); comment } *)
-
-(* let uninitialized_array ?comment (e : t) : t  = 
-  match e.expression_desc with 
-  | Number (Int {i = 0l; _}) -> array ?comment NA []
-  | _ -> {comment; expression_desc = Array_of_size e} *)
-
 
 module L = Literals
 (* Invariant: this is relevant to how we encode string
@@ -194,6 +187,7 @@ let typeof ?comment (e : t) : t =
     -> str ?comment L.js_type_string
   | Array _
     -> str ?comment L.js_type_object
+  | Bool _ -> str ?comment L.js_type_boolean
   | _ -> {expression_desc = Typeof e ; comment }
 
 
@@ -222,8 +216,6 @@ let math ?comment v args  : t =
    Used in [string_of_int] and format "%d"
    TODO: optimize
 *)
-let int_to_string ?comment (e : t) : t = 
-  {expression_desc = Anything_to_string e ; comment}
 
 (* Attention: Shared *mutable state* is evil, 
   [Js_fun_env.empty] is a mutable state ..
@@ -448,22 +440,10 @@ let char_to_int ?comment (v : t) : t =
   | Char_of_int v -> v 
   | _ -> {comment; expression_desc = Char_to_int v }
 
-let array_append ?comment e el : t = 
-  { comment ; expression_desc = Array_append (e, el)}
 
 let array_copy ?comment e : t = 
   { comment ; expression_desc = Array_copy e}
 
-(* Note that this return [undefined] in JS, 
-    it should be wrapped to avoid leak [undefined] into 
-    OCaml
-*)    
-let dump ?comment level el : t = 
-  {comment ; expression_desc = Dump(level,el)}
-
-(* let to_json_string ?comment e : t = 
-  { comment; expression_desc = Json_stringify e } *)
-
 let rec string_append ?comment (e : t) (el : t) : t = 
   match e.expression_desc , el.expression_desc  with 
   | Str(_,a), String_append ({expression_desc = Str(_,b)}, c) ->
@@ -474,8 +454,6 @@ let rec string_append ?comment (e : t) (el : t) : t =
     String_append ({expression_desc = Str(_,c)} ,d) ->
     string_append ?comment (string_append a (str (b ^ c))) d 
   | Str (_,a), Str (_,b) -> str ?comment (a ^ b)
-  | _, Anything_to_string b -> string_append ?comment e b 
-  | Anything_to_string b, _ -> string_append ?comment b el
   | _, _ -> {comment ; expression_desc = String_append(e,el)}
 
 
@@ -519,17 +497,17 @@ let float_mod ?comment e1 e2 : J.expression =
 *)
 let rec triple_equal ?comment (e0 : t) (e1 : t ) : t = 
   match e0.expression_desc, e1.expression_desc with
-  | Var (Id ({name = "undefined"|"null"} as id)), 
+  | (Null| Undefined), 
     (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ )
-    when Ext_ident.is_js id && no_side_effect e1 -> 
+    when  no_side_effect e1 -> 
     caml_false (* TODO: rename it as [caml_false] *)
   | 
     (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
-    | Fun _ | Array _ | Caml_block _ ),  Var (Id ({name = "undefined"|"null"; } as id))
-    when Ext_ident.is_js id && no_side_effect e0 -> 
+    | Fun _ | Array _ | Caml_block _ ),  (Null|Undefined)
+    when no_side_effect e0 -> 
     caml_false
   | Str (_,x), Str (_,y) ->  (* CF*)
     bool (Ext_string.equal x y)
@@ -543,6 +521,10 @@ let rec triple_equal ?comment (e0 : t) (e1 : t ) : t =
     bool (i0 = i1)      
   | Char_of_int a , Char_of_int b -> 
     triple_equal ?comment a b 
+  | Null, Undefined   
+  | Undefined, Null -> caml_false
+  | Null, Null
+  | Undefined, Undefined -> caml_true
   | _ -> 
      {expression_desc = Bin(EqEqEq, e0,e1); comment}
 
@@ -551,14 +533,7 @@ let bin ?comment (op : J.binop) e0 e1 : t =
   | EqEqEq -> triple_equal ?comment e0 e1
   | _ -> {expression_desc = Bin(op,e0,e1); comment}
 
-(* | (Bin (NotEqEq, e1,  *)
-(*         {expression_desc = Var (Id ({name = "undefined"; _} as id))}) *)
-(*   | Bin (NotEqEq,  *)
-(*          {expression_desc = Var (Id ({name = "undefined"; _} as id))},  *)
-(*          e1) *)
-(*   ),  *)
-(*   _ when Ext_ident.is_js id ->  *)
-(*   and_ e1 e2 *)
+
 (* TODO: Constant folding, Google Closure will do that?,
    Even if Google Clsoure can do that, we will see how it interact with other
    optimizations
@@ -775,11 +750,6 @@ let is_type_number ?comment (e : t) : t =
   string_equal ?comment (typeof e) (str "number")    
 
 
-let string_of_small_int_array ?comment xs : t = 
-  {expression_desc = String_of_small_int_array xs; comment}
-
-
-
 (* we are calling [Caml_primitive.primitive_name], since it's under our
    control, we should make it follow the javascript name convention, and
    call plain [dot]
@@ -841,7 +811,7 @@ let public_method_call meth_name obj label cache args =
 (*       [fn  ; arr NA args ]             *)
 (* ) *)
 
-let set_tag ?comment e tag : t = 
+let block_set_tag ?comment e tag : t = 
   seq {expression_desc = Caml_block_set_tag (e,tag); comment } unit 
 
 
@@ -1245,47 +1215,47 @@ let of_block ?comment ?e block : t =
             , Js_fun_env.empty 0)
     } []
 
-let is_null ?comment x = triple_equal ?comment x nil 
+let is_null ?comment (x : t) =   
+  triple_equal ?comment x nil 
 
 
 let is_undef ?comment x = triple_equal ?comment x undefined
 
 let for_sure_js_null_undefined (x : t) = 
   match x.expression_desc with 
-  | Var (Id ({name = "undefined" | "null"} as id)) 
-    -> Ext_ident.is_js id 
+  | Null | Undefined
+    -> true
   | _ -> false
   
 let is_null_undefined ?comment (x: t) : t = 
   match x.expression_desc with 
-  | Var (Id ({name = "undefined" | "null"} as id))
-    when Ext_ident.is_js id 
+  | Null | Undefined
     -> caml_true
   | Number _ | Array _ | Caml_block _ -> caml_false
-  | _ -> 
-     
+  | _ ->      
       { comment ; 
-        expression_desc = Is_null_undefined_to_boolean x 
+        expression_desc = Is_null_or_undefined x 
       }
 
 let eq_null_undefined_boolean ?comment (a : t) (b : t) = 
   match a.expression_desc, b.expression_desc with 
-  | Var (Id ({name = "null" | "undefined"} as id) ),   
+  | (Null | Undefined),   
     (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ )
-    when Ext_ident.is_js id -> 
+     -> 
     caml_false
   | (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ ), 
-      Var (Id ({name = "null" | "undefined"} as id) )
-    when Ext_ident.is_js id -> 
+      (Null | Undefined)
+     -> 
     caml_false
-  | Var (Id ({name = "null" | "undefined" as n1 } as id1) ), 
-    Var (Id ({name = "null" | "undefined" as n2 } as id2) )
-    when Ext_ident.is_js id1 && Ext_ident.is_js id2 
-   ->  bool (n1 = n2)    
+  | (Null, Undefined)
+  | (Undefined, Null) -> caml_false
+  | (Null, Null)
+  | (Undefined, Undefined)
+    -> caml_true
   | _ ->       
        {expression_desc = Bin(EqEqEq, a, b); comment}
     
@@ -1293,23 +1263,24 @@ let eq_null_undefined_boolean ?comment (a : t) (b : t) =
 
 let neq_null_undefined_boolean ?comment (a : t) (b : t) = 
   match a.expression_desc, b.expression_desc with 
-  | Var (Id ({name = "null" | "undefined"} as id) ),   
+  | (Null | Undefined),   
     (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ )
-    when Ext_ident.is_js id -> 
+     -> 
     caml_true
   | (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ ), 
-      Var (Id ({name = "null" | "undefined"} as id) )
-    when Ext_ident.is_js id -> 
+      (Null | Undefined)
+     -> 
     caml_true
-  | Var (Id ({name = "null" | "undefined" as n1 } as id1) ), 
-    Var (Id ({name = "null" | "undefined" as n2 } as id2) )
-    when Ext_ident.is_js id1 && Ext_ident.is_js id2 
-    ->   
-    if  n1 <> n2 then caml_true else caml_false
+  | (Null , Null )
+  | (Undefined, Undefined)
+   -> caml_false
+  | (Null, Undefined)
+  | (Undefined, Null)
+   -> caml_true
   | _ ->       
        {expression_desc = Bin(NotEqEq, a, b); comment}
 
diff --git a/jscomp/core/js_exp_make.mli b/jscomp/core/js_exp_make.mli
index 52a1ebad19..c8fc9b25f5 100644
--- a/jscomp/core/js_exp_make.mli
+++ b/jscomp/core/js_exp_make.mli
@@ -139,8 +139,6 @@ val array_length : unary_op
 
 val string_length : unary_op
 
-val string_of_small_int_array : unary_op
-
 val bytes_length :  unary_op
 
 val function_length : unary_op
@@ -148,9 +146,6 @@ val function_length : unary_op
 val char_of_int : unary_op
 
 val char_to_int : unary_op
-
-val array_append : binary_op
-
 val array_copy : unary_op
 val string_append : binary_op
 (**
@@ -249,15 +244,6 @@ val call : ?comment:string  -> info:Js_call_info.t -> t -> t list -> t
 
 val flat_call : binary_op
 
-val dump : ?comment:string -> Js_op.level -> t list -> t
-
-
-
-(** see {!https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Unary_plus}*)
-(* val to_number : unary_op *)
-val int_to_string : unary_op
-
-
 val new_ : ?comment:string -> J.expression -> J.expression list -> t
 
 val array : 
@@ -308,7 +294,7 @@ val is_caml_block : ?comment:string -> t -> t
 
 
 val tag : ?comment:string -> J.expression -> t
-val set_tag : ?comment:string -> J.expression -> J.expression -> t
+val block_set_tag : ?comment:string -> J.expression -> J.expression -> t
 
 (** Note that this is coupled with how we encode block, if we use the 
     `Object.defineProperty(..)` since the array already hold the length,
diff --git a/jscomp/core/js_fold.ml b/jscomp/core/js_fold.ml
index d5b2d7aa36..9540e705ac 100644
--- a/jscomp/core/js_fold.ml
+++ b/jscomp/core/js_fold.ml
@@ -125,54 +125,11 @@ class virtual fold =
        ]}       
      *)
                  (** where we use a trick [== null ] *)
-                 (* used in [#create_array] primitive, note having
-       uninitilized array is not as bad as in ocaml, 
-       since GC does not rely on it
-     *)
-                 (* shallow copy, like [x.slice] *)
-                 (* For [caml_array_append]*)
-                 (* | Tag_ml_obj of expression *) (* js true/false*)
+                 (* shallow copy, like [x.slice] *) (* js true/false*)
                  (* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence 
      [typeof] is an operator     
   *)
-                 (* !v *) (* String.fromCharCode.apply(null, args) *)
-                 (* Convert JS boolean into OCaml boolean 
-       like [+true], note this ast talks using js
-       terminnology unless explicity stated                       
-     *)
-                 (* TODO: in the future, it might make sense to group primitivie by type,
-     which makes optimizations easier
-     {[ JSON.stringify(value, replacer[, space]) ]}
-  *)
-                 (* for debugging utitlites, 
-     TODO:  [Dump] is not necessary with this primitive 
-     Note that the semantics is slightly different from [JSON.stringify]     
-     {[
-       JSON.stringify("x")       
-     ]}
-     {[
-       ""x""       
-     ]}     
-     {[
-       JSON.stringify(undefined)       
-     ]}     
-     {[
-       undefined       
-     ]}
-     {[ '' + undefined
-     ]}     
-     {[ 'undefined'
-     ]}     
-  *)
-                 (* TODO: 
-     add 
-     {[ Assert of bool * expression ]}     
-  *)
-                 (* to support 
-       val log1 : 'a -> unit
-       val log2 : 'a -> 'b -> unit 
-       val log3 : 'a -> 'b -> 'c -> unit 
-     *)
+                 (* !v *)
                  (* TODO: Add some primitives so that [js inliner] can do a better job *)
                  (* [int_op] will guarantee return [int32] bits 
      https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators  *)
@@ -182,10 +139,6 @@ class virtual fold =
        if it's know at compile time, we can turn it into
        f(args[0], args[1], ... )
      *)
-                 (* {[ Bind (a,b) ]}
-     is literally
-     {[ a.bind(b) ]}
-  *)
                  (* Analysze over J expression is hard since, 
         some primitive  call is translated 
         into a plain call, it's better to keep them
@@ -366,23 +319,13 @@ class virtual fold =
           let o = o#expression _x in let o = o#length_object _x_i1 in o
       | Char_of_int _x -> let o = o#expression _x in o
       | Char_to_int _x -> let o = o#expression _x in o
-      | Is_null_undefined_to_boolean _x -> let o = o#expression _x in o
-      | Array_of_size _x -> let o = o#expression _x in o
+      | Is_null_or_undefined _x -> let o = o#expression _x in o
       | Array_copy _x -> let o = o#expression _x in o
-      | Array_append (_x, _x_i1) ->
-          let o = o#expression _x in let o = o#expression _x_i1 in o
       | String_append (_x, _x_i1) ->
           let o = o#expression _x in let o = o#expression _x_i1 in o
-      | Anything_to_number _x -> let o = o#expression _x in o
       | Bool _x -> let o = o#bool _x in o
       | Typeof _x -> let o = o#expression _x in o
       | Js_not _x -> let o = o#expression _x in o
-      | String_of_small_int_array _x -> let o = o#expression _x in o
-      | Json_stringify _x -> let o = o#expression _x in o
-      | Anything_to_string _x -> let o = o#expression _x in o
-      | Dump (_x, _x_i1) ->
-          let o = o#unknown _x in
-          let o = o#list (fun o -> o#expression) _x_i1 in o
       | Seq (_x, _x_i1) ->
           let o = o#expression _x in let o = o#expression _x_i1 in o
       | Cond (_x, _x_i1, _x_i2) ->
@@ -393,8 +336,6 @@ class virtual fold =
           let o = o#expression _x_i1 in let o = o#expression _x_i2 in o
       | FlatCall (_x, _x_i1) ->
           let o = o#expression _x in let o = o#expression _x_i1 in o
-      | Bind (_x, _x_i1) ->
-          let o = o#expression _x in let o = o#expression _x_i1 in o
       | Call (_x, _x_i1, _x_i2) ->
           let o = o#expression _x in
           let o = o#list (fun o -> o#expression) _x_i1 in
@@ -433,6 +374,8 @@ class virtual fold =
           let o = o#expression _x in let o = o#expression _x_i1 in o
       | Number _x -> let o = o#number _x in o
       | Object _x -> let o = o#property_map _x in o
+      | Undefined -> o
+      | Null -> o
     method expression : expression -> 'self_type =
       fun { expression_desc = _x; comment = _x_i1 } ->
         let o = o#expression_desc _x in
diff --git a/jscomp/core/js_map.ml b/jscomp/core/js_map.ml
index 73c6f97b21..dfb241d0e8 100644
--- a/jscomp/core/js_map.ml
+++ b/jscomp/core/js_map.ml
@@ -138,54 +138,11 @@ class virtual map =
        ]}       
      *)
                  (** where we use a trick [== null ] *)
-                 (* used in [#create_array] primitive, note having
-       uninitilized array is not as bad as in ocaml, 
-       since GC does not rely on it
-     *)
-                 (* shallow copy, like [x.slice] *)
-                 (* For [caml_array_append]*)
-                 (* | Tag_ml_obj of expression *) (* js true/false*)
+                 (* shallow copy, like [x.slice] *) (* js true/false*)
                  (* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence 
      [typeof] is an operator     
   *)
-                 (* !v *) (* String.fromCharCode.apply(null, args) *)
-                 (* Convert JS boolean into OCaml boolean 
-       like [+true], note this ast talks using js
-       terminnology unless explicity stated                       
-     *)
-                 (* TODO: in the future, it might make sense to group primitivie by type,
-     which makes optimizations easier
-     {[ JSON.stringify(value, replacer[, space]) ]}
-  *)
-                 (* for debugging utitlites, 
-     TODO:  [Dump] is not necessary with this primitive 
-     Note that the semantics is slightly different from [JSON.stringify]     
-     {[
-       JSON.stringify("x")       
-     ]}
-     {[
-       ""x""       
-     ]}     
-     {[
-       JSON.stringify(undefined)       
-     ]}     
-     {[
-       undefined       
-     ]}
-     {[ '' + undefined
-     ]}     
-     {[ 'undefined'
-     ]}     
-  *)
-                 (* TODO: 
-     add 
-     {[ Assert of bool * expression ]}     
-  *)
-                 (* to support 
-       val log1 : 'a -> unit
-       val log2 : 'a -> 'b -> unit 
-       val log3 : 'a -> 'b -> 'c -> unit 
-     *)
+                 (* !v *)
                  (* TODO: Add some primitives so that [js inliner] can do a better job *)
                  (* [int_op] will guarantee return [int32] bits 
      https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators  *)
@@ -195,10 +152,6 @@ class virtual map =
        if it's know at compile time, we can turn it into
        f(args[0], args[1], ... )
      *)
-                 (* {[ Bind (a,b) ]}
-     is literally
-     {[ a.bind(b) ]}
-  *)
                  (* Analysze over J expression is hard since, 
         some primitive  call is translated 
         into a plain call, it's better to keep them
@@ -391,30 +344,15 @@ class virtual map =
           let _x_i1 = o#length_object _x_i1 in Length (_x, _x_i1)
       | Char_of_int _x -> let _x = o#expression _x in Char_of_int _x
       | Char_to_int _x -> let _x = o#expression _x in Char_to_int _x
-      | Is_null_undefined_to_boolean _x ->
-          let _x = o#expression _x in Is_null_undefined_to_boolean _x
-      | Array_of_size _x -> let _x = o#expression _x in Array_of_size _x
+      | Is_null_or_undefined _x ->
+          let _x = o#expression _x in Is_null_or_undefined _x
       | Array_copy _x -> let _x = o#expression _x in Array_copy _x
-      | Array_append (_x, _x_i1) ->
-          let _x = o#expression _x in
-          let _x_i1 = o#expression _x_i1 in Array_append (_x, _x_i1)
       | String_append (_x, _x_i1) ->
           let _x = o#expression _x in
           let _x_i1 = o#expression _x_i1 in String_append (_x, _x_i1)
-      | Anything_to_number _x ->
-          let _x = o#expression _x in Anything_to_number _x
       | Bool _x -> let _x = o#bool _x in Bool _x
       | Typeof _x -> let _x = o#expression _x in Typeof _x
       | Js_not _x -> let _x = o#expression _x in Js_not _x
-      | String_of_small_int_array _x ->
-          let _x = o#expression _x in String_of_small_int_array _x
-      | Json_stringify _x -> let _x = o#expression _x in Json_stringify _x
-      | Anything_to_string _x ->
-          let _x = o#expression _x in Anything_to_string _x
-      | Dump (_x, _x_i1) ->
-          let _x = o#unknown _x in
-          let _x_i1 = o#list (fun o -> o#expression) _x_i1
-          in Dump (_x, _x_i1)
       | Seq (_x, _x_i1) ->
           let _x = o#expression _x in
           let _x_i1 = o#expression _x_i1 in Seq (_x, _x_i1)
@@ -429,9 +367,6 @@ class virtual map =
       | FlatCall (_x, _x_i1) ->
           let _x = o#expression _x in
           let _x_i1 = o#expression _x_i1 in FlatCall (_x, _x_i1)
-      | Bind (_x, _x_i1) ->
-          let _x = o#expression _x in
-          let _x_i1 = o#expression _x_i1 in Bind (_x, _x_i1)
       | Call (_x, _x_i1, _x_i2) ->
           let _x = o#expression _x in
           let _x_i1 = o#list (fun o -> o#expression) _x_i1 in
@@ -481,6 +416,8 @@ class virtual map =
           let _x_i1 = o#expression _x_i1 in Caml_block_set_length (_x, _x_i1)
       | Number _x -> let _x = o#number _x in Number _x
       | Object _x -> let _x = o#property_map _x in Object _x
+      | Undefined -> Undefined
+      | Null -> Null
     method expression : expression -> expression =
       fun { expression_desc = _x; comment = _x_i1 } ->
         let _x = o#expression_desc _x in
diff --git a/jscomp/core/js_pass_tailcall_inline.ml b/jscomp/core/js_pass_tailcall_inline.ml
index 66e46e834c..a7faaeaabb 100644
--- a/jscomp/core/js_pass_tailcall_inline.ml
+++ b/jscomp/core/js_pass_tailcall_inline.ml
@@ -220,7 +220,7 @@ let subst name export_set stats  =
             (* Mark a function as dead means it will never be scanned, 
                here we inline the function
             *)
-            Ext_list.append block @@ self#block rest
+            Ext_list.append block (self#block rest)
           | (None | Some _) ->
             self#statement st :: self#block rest
         end
@@ -235,9 +235,8 @@ let subst name export_set stats  =
 
 
 let tailcall_inline (program : J.program) = 
-  let _stats = get_stats program in
-  let _export_set = program.export_set in
-  program
-  |> (subst program.name _export_set _stats )# program
-  (* |> pass_beta #program *)
+  let stats = get_stats program in
+  let export_set = program.export_set in
+  (subst program.name export_set stats )#program program
+
     
diff --git a/jscomp/core/js_stmt_make.ml b/jscomp/core/js_stmt_make.ml
index 67ce93164f..1fe3a70a9c 100644
--- a/jscomp/core/js_stmt_make.ml
+++ b/jscomp/core/js_stmt_make.ml
@@ -268,11 +268,7 @@ let rec if_ ?comment  ?declaration ?else_ (e : J.expression) (then_ : J.block)
     | Bin (Bor , {expression_desc = Number (Int { i = 0l ; _})}, a), _, _ 
       -> 
       aux ?comment a  then_ else_ acc
-    (* | Bin (NotEqEq, e1,  *)
-    (*        {expression_desc = Var (Id ({name = "undefined"; _} as id))}), *)
-    (*   _, _ *)
-    (*   when Ext_ident.is_js id ->  *)
-    (*   aux ?comment e1 then_ else_ acc  *)
+
 
     | ((Bin (Gt, 
              ({expression_desc = 
diff --git a/jscomp/core/lam.ml b/jscomp/core/lam.ml
index c2ac867eb2..41d0551219 100644
--- a/jscomp/core/lam.ml
+++ b/jscomp/core/lam.ml
@@ -197,9 +197,6 @@ type primitive =
   | Pis_null_undefined
   | Pjs_typeof
   | Pjs_function_length
-
-  | Pjs_string_of_small_array
-  (* | Pjs_is_instance_array *)
   | Pcaml_obj_length
   | Pcaml_obj_set_length
   | Pwrap_exn (* convert either JS exception or OCaml exception into OCaml format *)
@@ -1866,12 +1863,6 @@ let convert exports lam : _ * _  =
         | "#null_to_opt" -> Pnull_to_opt
         | "#is_nil_undef" -> Pis_null_undefined
         | "#string_append" -> Pstringadd
-
-
-        | "#string_of_small_int_array" -> Pjs_string_of_small_array
-        (* {[String.fromCharCode.apply(null,x)]}
-           Note if we have better suport [@bs.splice],
-           we can get rid of it*)
         | "#obj_set_length" -> Pcaml_obj_set_length
         | "#obj_length" -> Pcaml_obj_length
         | "#function_length" -> Pjs_function_length
diff --git a/jscomp/core/lam.mli b/jscomp/core/lam.mli
index ffaceb1949..1ce9907502 100644
--- a/jscomp/core/lam.mli
+++ b/jscomp/core/lam.mli
@@ -192,9 +192,6 @@ type primitive =
 
   | Pjs_typeof
   | Pjs_function_length 
-
-  | Pjs_string_of_small_array
-  (* | Pjs_is_instance_array *)
   | Pcaml_obj_length
   | Pcaml_obj_set_length
   | Pwrap_exn (* convert either JS exception or OCaml exception into OCaml format *)  
diff --git a/jscomp/core/lam_analysis.ml b/jscomp/core/lam_analysis.ml
index e0a6cb510a..6e422b940e 100644
--- a/jscomp/core/lam_analysis.ml
+++ b/jscomp/core/lam_analysis.ml
@@ -160,7 +160,6 @@ let rec no_side_effects (lam : Lam.t) : bool =
       (* | Pjs_is_instance_array *)
       | Pwrap_exn
         -> true
-      | Pjs_string_of_small_array
       | Pcaml_obj_set_length        
       | Pjs_apply
       | Pjs_runtime_apply
@@ -541,7 +540,7 @@ and eq_primitive ( lhs : Lam.primitive) (rhs : Lam.primitive) =
   | Pupdate_mod -> rhs = Pupdate_mod
   | Pbswap16 -> rhs = Pbswap16
   | Pjs_function_length -> rhs = Pjs_function_length
-  | Pjs_string_of_small_array -> rhs = Pjs_string_of_small_array
+  (* | Pjs_string_of_small_array -> rhs = Pjs_string_of_small_array *)
   (* | Pjs_is_instance_array -> rhs = Pjs_is_instance_array *)
   | Pcaml_obj_length -> rhs = Pcaml_obj_length
   | Pcaml_obj_set_length -> rhs = Pcaml_obj_set_length
diff --git a/jscomp/core/lam_compile_const.ml b/jscomp/core/lam_compile_const.ml
index 1182d7f013..5880a0f5e8 100644
--- a/jscomp/core/lam_compile_const.ml
+++ b/jscomp/core/lam_compile_const.ml
@@ -107,7 +107,7 @@ let translate_arg_cst (cst : External_arg_spec.cst) =
      E.int (Int32.of_int i)
    | Arg_string_lit i -> 
      E.str i
-   | Arg_js_null  -> E.raw_js_code Exp "null"
+   | Arg_js_null  -> E.nil
    | Arg_js_json s 
      -> E.raw_js_code Exp s
 
diff --git a/jscomp/core/lam_compile_external_call.ml b/jscomp/core/lam_compile_external_call.ml
index dee4fc6885..32b3e149d4 100644
--- a/jscomp/core/lam_compile_external_call.ml
+++ b/jscomp/core/lam_compile_external_call.ml
@@ -321,12 +321,8 @@ let translate_ffi
        2. support [@@bs.scope "window"]
        we need know whether we should call [add_js_module] or not 
     *)
-    begin match name, handle_external_opt external_module_name , scopes with 
-      | "null", None, [] -> E.nil 
-      | "undefined", None, [] -> E.undefined
-      | _, _, _ -> 
-        translate_scoped_module_val external_module_name name scopes
-    end
+      translate_scoped_module_val external_module_name name scopes
+
   | Js_send {splice  = js_splice ; name ; pipe = false; js_send_scopes = scopes } -> 
     begin match args  with
       | self :: args -> 
diff --git a/jscomp/core/lam_compile_primitive.ml b/jscomp/core/lam_compile_primitive.ml
index 54fbbb956f..94d3b78636 100644
--- a/jscomp/core/lam_compile_primitive.ml
+++ b/jscomp/core/lam_compile_primitive.ml
@@ -75,8 +75,8 @@ let translate  loc
     begin match args with 
       | [e] -> 
         begin match e.expression_desc with 
-          | Var _ -> 
-            E.econd (E.is_null e) Js_of_lam_option.none (Js_of_lam_option.some e)
+          | Var _ | Undefined | Null -> 
+            E.econd (E.is_null e) Js_of_lam_option.none (Js_of_lam_option.some e)           
           | _ ->
             E.runtime_call Js_runtime_modules.js_primitive
               "null_to_opt" args 
@@ -93,7 +93,7 @@ let translate  loc
     begin match args with 
       | [e] -> 
         begin match e.expression_desc with 
-          | Var _ -> 
+          | Var _ | Undefined | Null -> 
             E.econd (E.is_undef e) Js_of_lam_option.none (Js_of_lam_option.some e)
           | _ -> 
             E.runtime_call Js_runtime_modules.js_primitive  
@@ -111,7 +111,7 @@ let translate  loc
     begin match args with 
       | [e] -> 
         begin match e.expression_desc with 
-          | Var _ -> 
+          | Var _ | Undefined | Null   -> 
             E.econd (E.is_null_undefined e) 
               Js_of_lam_option.none 
               (Js_of_lam_option.some e)
@@ -137,18 +137,6 @@ let translate  loc
       | [a;b] -> E.set_length a b 
       | _ -> assert false 
     end
-  | Lam.Pjs_string_of_small_array -> 
-    begin match args with 
-      | [e] -> E.string_of_small_int_array e 
-      | _ -> assert false 
-    end 
-  (* | Lam.Pjs_is_instance_array -> 
-    begin match args with 
-      | [e] -> E.is_instance_array e 
-      | _ -> assert false 
-    end  *)
-
-
   | Pis_null -> 
     begin match args with 
       | [e] -> E.is_null e 
@@ -703,9 +691,7 @@ let translate  loc
   (*   assert false (\* already handled *\) *)
   (* assert false *)
   | Pduprecord ((Record_regular 
-                | Record_float ),0)
-  | Pduprecord ((Record_regular 
-                | Record_float ),_) -> 
+                | Record_float ),_size) -> (* _size is the length of all_lables*)
     begin match args with 
       | [e] -> Js_of_lam_record.copy e
       | _ -> assert false       
diff --git a/jscomp/core/lam_dispatch_primitive.ml b/jscomp/core/lam_dispatch_primitive.ml
index 2c4b743ede..ed743d3aea 100644
--- a/jscomp/core/lam_dispatch_primitive.ml
+++ b/jscomp/core/lam_dispatch_primitive.ml
@@ -138,13 +138,6 @@ let translate loc (prim_name : string)
     | "caml_power_float"  -> 
       E.math "pow" args
 
-
-    | "caml_array_append" -> 
-      begin match args with 
-        | [e0;e1] -> E.array_append e0 e1
-        | _ ->  assert false 
-      end
-
     | "caml_array_get" -> 
       call Js_runtime_modules.array
     | "caml_array_get_addr"
@@ -659,8 +652,6 @@ let translate loc (prim_name : string)
             *)
             | _ -> E.array_copy a
           end
-        (* if Js_analyzer.is_constant a then a
-           else E.array_copy a *)
         | _ -> assert false 
       end
     | "caml_obj_block" -> 
@@ -694,20 +685,11 @@ let translate loc (prim_name : string)
     | "caml_nativeint_of_string" 
     | "caml_int64_format"
     | "caml_int64_of_string"
+    | "caml_format_int" 
       -> 
       call Js_runtime_modules.format 
-    | "caml_format_int" -> 
-      begin match args with 
-        | [ {expression_desc = Str (_, "%d"); _}; v] 
-          ->
-          E.int_to_string v 
-        | _ -> 
-          call Js_runtime_modules.format
-      end
     (*   "caml_alloc_dummy"; *)
     (* TODO:   "caml_alloc_dummy_float"; *)
-
-
     | "caml_obj_is_block"
       -> 
       begin match args with 
@@ -764,7 +746,7 @@ let translate loc (prim_name : string)
       call Js_runtime_modules.obj_runtime
     | "caml_obj_set_tag" 
       -> begin match args with 
-          | [a;b]  -> E.set_tag a b 
+          | [a;b]  -> E.block_set_tag a b 
           | _ -> assert false end
     | "caml_obj_tag" -> 
       (* Note that in ocaml, [int] has tag [1000] and [string] has tag [252]
diff --git a/jscomp/core/lam_print.ml b/jscomp/core/lam_print.ml
index caedd92592..f596576eb3 100644
--- a/jscomp/core/lam_print.ml
+++ b/jscomp/core/lam_print.ml
@@ -108,8 +108,6 @@ let primitive ppf (prim : Lam.primitive) = match prim with
   (* | Pcreate_exception s -> fprintf ppf "[exn-create]%S" s  *)
   | Pcreate_extension s -> fprintf ppf "[ext-create]%S" s 
   | Pwrap_exn -> fprintf ppf "#exn"
-  | Pjs_string_of_small_array -> fprintf ppf "#string_of_small_array"
-  (* | Pjs_is_instance_array -> fprintf ppf "#is_instance_array" *)
   | Pcaml_obj_length -> fprintf ppf "#obj_length"
   | Pcaml_obj_set_length -> fprintf ppf "#obj_set_length"
   | Pinit_mod -> fprintf ppf "init_mod!"
diff --git a/jscomp/ext/ext_ident.ml b/jscomp/ext/ext_ident.ml
index ea98bdd93a..33c17448e0 100644
--- a/jscomp/ext/ext_ident.ml
+++ b/jscomp/ext/ext_ident.ml
@@ -312,9 +312,6 @@ let reset () =
   String_hashtbl.clear js_module_table
 
 
-let undefined = create_js "undefined"
-let nil = create_js "null"
-
 (* Has to be total order, [x < y]
    and [x > y] should be consistent
    flags are not relevant here
diff --git a/jscomp/ext/ext_ident.mli b/jscomp/ext/ext_ident.mli
index adb286b2d7..90869c55a3 100644
--- a/jscomp/ext/ext_ident.mli
+++ b/jscomp/ext/ext_ident.mli
@@ -56,9 +56,9 @@ val make_unused : unit -> Ident.t
 val convert : string -> string
 
 
-val undefined : Ident.t 
+
 val is_js_or_global : Ident.t -> bool
- val nil : Ident.t 
+
 
 
 val compare : Ident.t -> Ident.t -> int
diff --git a/jscomp/ext/literals.ml b/jscomp/ext/literals.ml
index 47ce84cccd..09e01835eb 100644
--- a/jscomp/ext/literals.ml
+++ b/jscomp/ext/literals.ml
@@ -32,6 +32,7 @@ let js_array_ctor = "Array"
 let js_type_number = "number"
 let js_type_string = "string"
 let js_type_object = "object" 
+let js_type_boolean = "boolean"
 let js_undefined = "undefined"
 let js_prop_length = "length"
 
diff --git a/jscomp/ext/literals.mli b/jscomp/ext/literals.mli
index d3e3de6980..c298775c0c 100644
--- a/jscomp/ext/literals.mli
+++ b/jscomp/ext/literals.mli
@@ -31,6 +31,7 @@ val js_array_ctor : string
 val js_type_number : string
 val js_type_string : string
 val js_type_object : string
+val js_type_boolean : string
 val js_undefined : string
 val js_prop_length : string
 
diff --git a/jscomp/others/js_null_undefined.ml b/jscomp/others/js_null_undefined.ml
index c4d10ad0d4..0d19d58017 100644
--- a/jscomp/others/js_null_undefined.ml
+++ b/jscomp/others/js_null_undefined.ml
@@ -29,8 +29,8 @@ external toOption : 'a t -> 'a option = "#null_undefined_to_opt"
 external to_opt : 'a t -> 'a option = "#null_undefined_to_opt"
 external return : 'a -> 'a t = "%identity"
 external test : 'a t -> bool =  "#is_nil_undef"
-external null : 'a t = "null" [@@bs.val]
-external undefined : 'a t = "undefined" [@@bs.val]
+external null : 'a t = "#null" 
+external undefined : 'a t = "#undefined"
 
 let bind x f =
   match to_opt x with
diff --git a/jscomp/others/js_null_undefined.mli b/jscomp/others/js_null_undefined.mli
index 6dd23b350c..56fadbff75 100644
--- a/jscomp/others/js_null_undefined.mli
+++ b/jscomp/others/js_null_undefined.mli
@@ -34,10 +34,10 @@ external return : 'a -> 'a t = "%identity"
 external test : 'a t -> bool =  "#is_nil_undef"
 
 (** The [null] value of type ['a Js.null_undefined]*)
-external null : 'a t = "null" [@@bs.val]
+external null : 'a t = "#null"
 
 (** The [undefined] value of type ['a Js.null_undefined] *)
-external undefined : 'a t = "undefined" [@@bs.val]
+external undefined : 'a t = "#undefined"
 
 
 
diff --git a/jscomp/runtime/bs_string.ml b/jscomp/runtime/bs_string.ml
index 69647a3f07..5be372dab5 100644
--- a/jscomp/runtime/bs_string.ml
+++ b/jscomp/runtime/bs_string.ml
@@ -45,8 +45,17 @@ external slice_rest : string -> int -> string = "slice"
 external index_of : string -> string -> int = "indexOf"
     [@@bs.send]
 external append : string -> string -> string = "#string_append"
-external of_small_int_array : int array -> string = "#string_of_small_int_array"
-external of_small_int32_array : int32 array -> string = "#string_of_small_int_array"
+external of_small_int_array :  
+    (_ [@bs.as {json|null|json}] ) -> 
+    int array -> string = 
+    "String.fromCharCode.apply" 
+[@@bs.val]
+
+external of_small_int32_array : 
+    int32 array -> string = 
+    "String.fromCharCode" 
+[@@bs.val] [@@bs.splice]   
+
 external lastIndexOf : string -> string -> int = "lastIndexOf"
 [@@bs.send]    
 external of_any : 'a -> string = "String"
diff --git a/jscomp/stdlib/array.ml b/jscomp/stdlib/array.ml
index 243eeade17..8d6d5aadcd 100644
--- a/jscomp/stdlib/array.ml
+++ b/jscomp/stdlib/array.ml
@@ -21,7 +21,12 @@ external unsafe_set: 'a array -> int -> 'a -> unit = "%array_unsafe_set"
 external make: int -> 'a -> 'a array = "caml_make_vect"
 external create: int -> 'a -> 'a array = "caml_make_vect"
 external unsafe_sub : 'a array -> int -> int -> 'a array = "caml_array_sub"
+#if BS then
+external append_prim : 'a array -> 'a array -> 'a array = "concat"
+[@@bs.send]
+#else
 external append_prim : 'a array -> 'a array -> 'a array = "caml_array_append"
+#end
 external concat : 'a array list -> 'a array = "caml_array_concat"
 external unsafe_blit :
   'a array -> int -> 'a array -> int -> int -> unit = "caml_array_blit"
diff --git a/jscomp/test/.depend b/jscomp/test/.depend
index ab49dcecc2..38d30d61b0 100644
--- a/jscomp/test/.depend
+++ b/jscomp/test/.depend
@@ -311,6 +311,7 @@ gpr_2614_test.cmj :
 gpr_2633_test.cmj :
 gpr_2642_test.cmj :
 gpr_2652_test.cmj : ../others/node.cmj ../stdlib/buffer.cmj
+gpr_2700_test.cmj :
 gpr_405_test.cmj : ../stdlib/hashtbl.cmj gpr_405_test.cmi
 gpr_441.cmj :
 gpr_459_test.cmj : mt.cmj
diff --git a/jscomp/test/Makefile b/jscomp/test/Makefile
index 52fcd4a8db..105721d2d1 100644
--- a/jscomp/test/Makefile
+++ b/jscomp/test/Makefile
@@ -249,6 +249,7 @@ OTHERS := test_literals a test_ari test_export2 test_internalOO test_obj_simple_
 	gpr_2642_test\
 	gpr_2652_test\
 	gpr_2614_test\
+	gpr_2700_test\
 # bs_uncurry_test
 # needs Lam to get rid of Uncurry arity first
 # simple_derive_test
diff --git a/jscomp/test/bang_primitive.js b/jscomp/test/bang_primitive.js
index 02db9387b8..1de53f634d 100644
--- a/jscomp/test/bang_primitive.js
+++ b/jscomp/test/bang_primitive.js
@@ -14,7 +14,7 @@ function test(x, y) {
 
 function f(x, _) {
   return /* tuple */[
-          String.fromCharCode.apply(null,x),
+          String.fromCharCode.apply(null, x),
           0
         ];
 }
diff --git a/jscomp/test/bang_primitive.ml b/jscomp/test/bang_primitive.ml
index 447f214a7a..1c6ab6d23e 100644
--- a/jscomp/test/bang_primitive.ml
+++ b/jscomp/test/bang_primitive.ml
@@ -35,7 +35,12 @@ external append : 'a array -> 'a array -> 'a array = "#array_append"
 let f x y = append x y
 *)
 
-external of_small_int_array : int array -> string = "#string_of_small_int_array"
+external of_small_int_array :  
+    (_ [@bs.as {json|null|json}] ) -> 
+    int array -> string = 
+    "String.fromCharCode.apply" 
+[@@bs.val]
+
 (* external string_of_char : char -> string = "#string_of_char" *)
 (* string_of_char y  *)
 
diff --git a/jscomp/test/gpr_1484.js b/jscomp/test/gpr_1484.js
index c0e9fac5f8..27e856c65c 100644
--- a/jscomp/test/gpr_1484.js
+++ b/jscomp/test/gpr_1484.js
@@ -2,7 +2,7 @@
 
 
 function test(x) {
-  x.nodeValue = (null);
+  x.nodeValue = null;
   return /* () */0;
 }
 
diff --git a/jscomp/test/gpr_2700_test.js b/jscomp/test/gpr_2700_test.js
new file mode 100644
index 0000000000..886e951c8a
--- /dev/null
+++ b/jscomp/test/gpr_2700_test.js
@@ -0,0 +1,13 @@
+'use strict';
+
+
+function f(x) {
+  if (x === 3) {
+    return true;
+  } else {
+    return x === 4;
+  }
+}
+
+exports.f = f;
+/* No side effect */
diff --git a/jscomp/test/gpr_2700_test.ml b/jscomp/test/gpr_2700_test.ml
new file mode 100644
index 0000000000..a08820c13c
--- /dev/null
+++ b/jscomp/test/gpr_2700_test.ml
@@ -0,0 +1,4 @@
+
+
+
+let f x = x = 3 || x = 4
\ No newline at end of file
diff --git a/jscomp/test/js_null_test.js b/jscomp/test/js_null_test.js
index f24ae1a333..0ba403c824 100644
--- a/jscomp/test/js_null_test.js
+++ b/jscomp/test/js_null_test.js
@@ -10,7 +10,7 @@ var suites_000 = /* tuple */[
   (function () {
       return /* Eq */Block.__(0, [
                 /* None */0,
-                null === null ? /* None */0 : [null]
+                /* None */0
               ]);
     })
 ];
@@ -31,7 +31,7 @@ var suites_001 = /* :: */[
       (function () {
           return /* Eq */Block.__(0, [
                     /* None */0,
-                    null === null ? /* None */0 : [null]
+                    /* None */0
                   ]);
         })
     ],
diff --git a/jscomp/test/js_undefined_test.js b/jscomp/test/js_undefined_test.js
index 826cee0da4..7f8e79b5d4 100644
--- a/jscomp/test/js_undefined_test.js
+++ b/jscomp/test/js_undefined_test.js
@@ -10,7 +10,7 @@ var suites_000 = /* tuple */[
   (function () {
       return /* Eq */Block.__(0, [
                 /* None */0,
-                undefined === undefined ? /* None */0 : [undefined]
+                /* None */0
               ]);
     })
 ];
diff --git a/jscomp/test/test_per.js b/jscomp/test/test_per.js
index 900e09542b..b9f793f670 100644
--- a/jscomp/test/test_per.js
+++ b/jscomp/test/test_per.js
@@ -131,7 +131,7 @@ function bool_of_string(param) {
 }
 
 function string_of_int(n) {
-  return "" + n;
+  return Caml_format.caml_format_int("%d", n);
 }
 
 function valid_float_lexem(s) {
@@ -438,7 +438,7 @@ function print_bytes(s) {
 }
 
 function print_int(i) {
-  return output_string(stdout, "" + i);
+  return output_string(stdout, Caml_format.caml_format_int("%d", i));
 }
 
 function print_float(f) {
@@ -469,7 +469,7 @@ function prerr_bytes(s) {
 }
 
 function prerr_int(i) {
-  return output_string(stderr, "" + i);
+  return output_string(stderr, Caml_format.caml_format_int("%d", i));
 }
 
 function prerr_float(f) {
diff --git a/lib/bsb.ml b/lib/bsb.ml
index a5a83c7bac..be71463476 100644
--- a/lib/bsb.ml
+++ b/lib/bsb.ml
@@ -3376,6 +3376,7 @@ val js_array_ctor : string
 val js_type_number : string
 val js_type_string : string
 val js_type_object : string
+val js_type_boolean : string
 val js_undefined : string
 val js_prop_length : string
 
@@ -3510,6 +3511,7 @@ let js_array_ctor = "Array"
 let js_type_number = "number"
 let js_type_string = "string"
 let js_type_object = "object" 
+let js_type_boolean = "boolean"
 let js_undefined = "undefined"
 let js_prop_length = "length"
 
diff --git a/lib/bsb_helper.ml b/lib/bsb_helper.ml
index ef1c0a26b8..9ac1a2792c 100644
--- a/lib/bsb_helper.ml
+++ b/lib/bsb_helper.ml
@@ -3360,6 +3360,7 @@ val js_array_ctor : string
 val js_type_number : string
 val js_type_string : string
 val js_type_object : string
+val js_type_boolean : string
 val js_undefined : string
 val js_prop_length : string
 
@@ -3494,6 +3495,7 @@ let js_array_ctor = "Array"
 let js_type_number = "number"
 let js_type_string = "string"
 let js_type_object = "object" 
+let js_type_boolean = "boolean"
 let js_undefined = "undefined"
 let js_prop_length = "length"
 
diff --git a/lib/bsdep.ml b/lib/bsdep.ml
index 3fca73d989..150034bf45 100644
--- a/lib/bsdep.ml
+++ b/lib/bsdep.ml
@@ -27873,6 +27873,7 @@ val js_array_ctor : string
 val js_type_number : string
 val js_type_string : string
 val js_type_object : string
+val js_type_boolean : string
 val js_undefined : string
 val js_prop_length : string
 
@@ -28007,6 +28008,7 @@ let js_array_ctor = "Array"
 let js_type_number = "number"
 let js_type_string = "string"
 let js_type_object = "object" 
+let js_type_boolean = "boolean"
 let js_undefined = "undefined"
 let js_prop_length = "length"
 
diff --git a/lib/bsppx.ml b/lib/bsppx.ml
index 277b4109f7..d736f918a1 100644
--- a/lib/bsppx.ml
+++ b/lib/bsppx.ml
@@ -9815,6 +9815,7 @@ val js_array_ctor : string
 val js_type_number : string
 val js_type_string : string
 val js_type_object : string
+val js_type_boolean : string
 val js_undefined : string
 val js_prop_length : string
 
@@ -9949,6 +9950,7 @@ let js_array_ctor = "Array"
 let js_type_number = "number"
 let js_type_string = "string"
 let js_type_object = "object" 
+let js_type_boolean = "boolean"
 let js_undefined = "undefined"
 let js_prop_length = "length"
 
diff --git a/lib/js/array.js b/lib/js/array.js
index a7dfc2ecef..185d81e57d 100644
--- a/lib/js/array.js
+++ b/lib/js/array.js
@@ -279,7 +279,7 @@ function sort(cmp, a) {
               Caml_builtin_exceptions.assert_failure,
               [
                 "array.ml",
-                168,
+                173,
                 4
               ]
             ];
diff --git a/lib/js/caml_string.js b/lib/js/caml_string.js
index 993e015fbf..a80b7e3143 100644
--- a/lib/js/caml_string.js
+++ b/lib/js/caml_string.js
@@ -129,14 +129,14 @@ function bytes_to_string(a) {
   var s = "";
   var s_len = len;
   if (i === 0 && len <= 4096 && len === bytes.length) {
-    return String.fromCharCode.apply(null,bytes);
+    return String.fromCharCode.apply(null, bytes);
   } else {
     var offset = 0;
     while(s_len > 0) {
       var next = s_len < 1024 ? s_len : 1024;
       var tmp_bytes = new Array(next);
       caml_blit_bytes(bytes, offset, tmp_bytes, 0, next);
-      s = s + String.fromCharCode.apply(null,tmp_bytes);
+      s = s + String.fromCharCode.apply(null, tmp_bytes);
       s_len = s_len - next | 0;
       offset = offset + next | 0;
     };
diff --git a/lib/whole_compiler.ml b/lib/whole_compiler.ml
index ea1d40da01..4ba0f25a58 100644
--- a/lib/whole_compiler.ml
+++ b/lib/whole_compiler.ml
@@ -24857,6 +24857,7 @@ val js_array_ctor : string
 val js_type_number : string
 val js_type_string : string
 val js_type_object : string
+val js_type_boolean : string
 val js_undefined : string
 val js_prop_length : string
 
@@ -24991,6 +24992,7 @@ let js_array_ctor = "Array"
 let js_type_number = "number"
 let js_type_string = "string"
 let js_type_object = "object" 
+let js_type_boolean = "boolean"
 let js_undefined = "undefined"
 let js_prop_length = "length"
 
@@ -60340,9 +60342,9 @@ val make_unused : unit -> Ident.t
 val convert : string -> string
 
 
-val undefined : Ident.t 
+
 val is_js_or_global : Ident.t -> bool
- val nil : Ident.t 
+
 
 
 val compare : Ident.t -> Ident.t -> int
@@ -60664,9 +60666,6 @@ let reset () =
   String_hashtbl.clear js_module_table
 
 
-let undefined = create_js "undefined"
-let nil = create_js "null"
-
 (* Has to be total order, [x < y]
    and [x > y] should be consistent
    flags are not relevant here
@@ -63301,68 +63300,17 @@ and expression_desc =
   | Length of expression * length_object
   | Char_of_int of expression
   | Char_to_int of expression 
-  | Is_null_undefined_to_boolean of expression 
+  | Is_null_or_undefined of expression 
     (** where we use a trick [== null ] *)
-  | Array_of_size of expression 
-    (* used in [#create_array] primitive, note having
-       uninitilized array is not as bad as in ocaml, 
-       since GC does not rely on it
-     *)
   | Array_copy of expression (* shallow copy, like [x.slice] *)
-  | Array_append of expression * expression (* For [caml_array_append]*)
-  (* | Tag_ml_obj of expression *)
-  | String_append of expression * expression 
 
-  | Anything_to_number of expression
+  | String_append of expression * expression 
   | Bool of bool (* js true/false*)
   (* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence 
      [typeof] is an operator     
   *)
   | Typeof of expression
   | Js_not of expression (* !v *)
-  | String_of_small_int_array of expression 
-    (* String.fromCharCode.apply(null, args) *)
-    (* Convert JS boolean into OCaml boolean 
-       like [+true], note this ast talks using js
-       terminnology unless explicity stated                       
-     *)
-  | Json_stringify of expression 
-  (* TODO: in the future, it might make sense to group primitivie by type,
-     which makes optimizations easier
-     {[ JSON.stringify(value, replacer[, space]) ]}
-  *)
-  | Anything_to_string of expression
-  (* for debugging utitlites, 
-     TODO:  [Dump] is not necessary with this primitive 
-     Note that the semantics is slightly different from [JSON.stringify]     
-     {[
-       JSON.stringify("x")       
-     ]}
-     {[
-       ""x""       
-     ]}     
-     {[
-       JSON.stringify(undefined)       
-     ]}     
-     {[
-       undefined       
-     ]}
-     {[ '' + undefined
-     ]}     
-     {[ 'undefined'
-     ]}     
-  *)      
-  | Dump of Js_op.level * expression list
-  (* TODO: 
-     add 
-     {[ Assert of bool * expression ]}     
-  *)              
-    (* to support 
-       val log1 : 'a -> unit
-       val log2 : 'a -> 'b -> unit 
-       val log3 : 'a -> 'b -> 'c -> unit 
-     *)
-
   (* TODO: Add some primitives so that [js inliner] can do a better job *)  
   | Seq of expression * expression
   | Cond of expression * expression * expression
@@ -63377,11 +63325,6 @@ and expression_desc =
        if it's know at compile time, we can turn it into
        f(args[0], args[1], ... )
      *)
-  | Bind of expression * expression
-  (* {[ Bind (a,b) ]}
-     is literally
-     {[ a.bind(b) ]}
-  *)
   | Call of expression * expression list * Js_call_info.t
     (* Analysze over J expression is hard since, 
         some primitive  call is translated 
@@ -63449,7 +63392,8 @@ and expression_desc =
   *)      
   | Number of number
   | Object of property_map
-
+  | Undefined 
+  | Null
 and for_ident_expression = expression (* pure*)
 
 and finish_ident_expression = expression (* pure *)
@@ -66747,9 +66691,6 @@ type primitive =
 
   | Pjs_typeof
   | Pjs_function_length 
-
-  | Pjs_string_of_small_array
-  (* | Pjs_is_instance_array *)
   | Pcaml_obj_length
   | Pcaml_obj_set_length
   | Pwrap_exn (* convert either JS exception or OCaml exception into OCaml format *)  
@@ -67110,9 +67051,6 @@ type primitive =
   | Pis_null_undefined
   | Pjs_typeof
   | Pjs_function_length
-
-  | Pjs_string_of_small_array
-  (* | Pjs_is_instance_array *)
   | Pcaml_obj_length
   | Pcaml_obj_set_length
   | Pwrap_exn (* convert either JS exception or OCaml exception into OCaml format *)
@@ -68779,12 +68717,6 @@ let convert exports lam : _ * _  =
         | "#null_to_opt" -> Pnull_to_opt
         | "#is_nil_undef" -> Pis_null_undefined
         | "#string_append" -> Pstringadd
-
-
-        | "#string_of_small_int_array" -> Pjs_string_of_small_array
-        (* {[String.fromCharCode.apply(null,x)]}
-           Note if we have better suport [@bs.splice],
-           we can get rid of it*)
         | "#obj_set_length" -> Pcaml_obj_set_length
         | "#obj_length" -> Pcaml_obj_length
         | "#function_length" -> Pjs_function_length
@@ -69613,54 +69545,11 @@ class virtual fold =
        ]}       
      *)
                  (** where we use a trick [== null ] *)
-                 (* used in [#create_array] primitive, note having
-       uninitilized array is not as bad as in ocaml, 
-       since GC does not rely on it
-     *)
-                 (* shallow copy, like [x.slice] *)
-                 (* For [caml_array_append]*)
-                 (* | Tag_ml_obj of expression *) (* js true/false*)
+                 (* shallow copy, like [x.slice] *) (* js true/false*)
                  (* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence 
      [typeof] is an operator     
   *)
-                 (* !v *) (* String.fromCharCode.apply(null, args) *)
-                 (* Convert JS boolean into OCaml boolean 
-       like [+true], note this ast talks using js
-       terminnology unless explicity stated                       
-     *)
-                 (* TODO: in the future, it might make sense to group primitivie by type,
-     which makes optimizations easier
-     {[ JSON.stringify(value, replacer[, space]) ]}
-  *)
-                 (* for debugging utitlites, 
-     TODO:  [Dump] is not necessary with this primitive 
-     Note that the semantics is slightly different from [JSON.stringify]     
-     {[
-       JSON.stringify("x")       
-     ]}
-     {[
-       ""x""       
-     ]}     
-     {[
-       JSON.stringify(undefined)       
-     ]}     
-     {[
-       undefined       
-     ]}
-     {[ '' + undefined
-     ]}     
-     {[ 'undefined'
-     ]}     
-  *)
-                 (* TODO: 
-     add 
-     {[ Assert of bool * expression ]}     
-  *)
-                 (* to support 
-       val log1 : 'a -> unit
-       val log2 : 'a -> 'b -> unit 
-       val log3 : 'a -> 'b -> 'c -> unit 
-     *)
+                 (* !v *)
                  (* TODO: Add some primitives so that [js inliner] can do a better job *)
                  (* [int_op] will guarantee return [int32] bits 
      https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators  *)
@@ -69670,10 +69559,6 @@ class virtual fold =
        if it's know at compile time, we can turn it into
        f(args[0], args[1], ... )
      *)
-                 (* {[ Bind (a,b) ]}
-     is literally
-     {[ a.bind(b) ]}
-  *)
                  (* Analysze over J expression is hard since, 
         some primitive  call is translated 
         into a plain call, it's better to keep them
@@ -69854,23 +69739,13 @@ class virtual fold =
           let o = o#expression _x in let o = o#length_object _x_i1 in o
       | Char_of_int _x -> let o = o#expression _x in o
       | Char_to_int _x -> let o = o#expression _x in o
-      | Is_null_undefined_to_boolean _x -> let o = o#expression _x in o
-      | Array_of_size _x -> let o = o#expression _x in o
+      | Is_null_or_undefined _x -> let o = o#expression _x in o
       | Array_copy _x -> let o = o#expression _x in o
-      | Array_append (_x, _x_i1) ->
-          let o = o#expression _x in let o = o#expression _x_i1 in o
       | String_append (_x, _x_i1) ->
           let o = o#expression _x in let o = o#expression _x_i1 in o
-      | Anything_to_number _x -> let o = o#expression _x in o
       | Bool _x -> let o = o#bool _x in o
       | Typeof _x -> let o = o#expression _x in o
       | Js_not _x -> let o = o#expression _x in o
-      | String_of_small_int_array _x -> let o = o#expression _x in o
-      | Json_stringify _x -> let o = o#expression _x in o
-      | Anything_to_string _x -> let o = o#expression _x in o
-      | Dump (_x, _x_i1) ->
-          let o = o#unknown _x in
-          let o = o#list (fun o -> o#expression) _x_i1 in o
       | Seq (_x, _x_i1) ->
           let o = o#expression _x in let o = o#expression _x_i1 in o
       | Cond (_x, _x_i1, _x_i2) ->
@@ -69881,8 +69756,6 @@ class virtual fold =
           let o = o#expression _x_i1 in let o = o#expression _x_i2 in o
       | FlatCall (_x, _x_i1) ->
           let o = o#expression _x in let o = o#expression _x_i1 in o
-      | Bind (_x, _x_i1) ->
-          let o = o#expression _x in let o = o#expression _x_i1 in o
       | Call (_x, _x_i1, _x_i2) ->
           let o = o#expression _x in
           let o = o#list (fun o -> o#expression) _x_i1 in
@@ -69921,6 +69794,8 @@ class virtual fold =
           let o = o#expression _x in let o = o#expression _x_i1 in o
       | Number _x -> let o = o#number _x in o
       | Object _x -> let o = o#property_map _x in o
+      | Undefined -> o
+      | Null -> o
     method expression : expression -> 'self_type =
       fun { expression_desc = _x; comment = _x_i1 } ->
         let o = o#expression_desc _x in
@@ -70138,13 +70013,15 @@ let free_variables_of_expression used_idents defined_idents st =
 
 let rec no_side_effect_expression_desc (x : J.expression_desc)  = 
   match x with 
+  | Undefined
+  | Null
   | Bool _ 
   | Var _ 
   | Unicode _ -> true 
   | Fun _ -> true
   | Number _ -> true (* Can be refined later *)
   | Access (a,b) -> no_side_effect a && no_side_effect b 
-  | Is_null_undefined_to_boolean b -> no_side_effect b 
+  | Is_null_or_undefined b -> no_side_effect b 
   | Str (b,_) -> b    
   | Array (xs,_mutable_flag)  
   | Caml_block (xs, _mutable_flag, _, _)
@@ -70155,10 +70032,8 @@ let rec no_side_effect_expression_desc (x : J.expression_desc)  =
         the block is mutable does not mean this operation is non-pure
     *)
     List.for_all no_side_effect  xs 
-  | Bind(fn, obj) -> no_side_effect fn && no_side_effect obj
   | Object kvs -> 
     List.for_all (fun (_property_name, y) -> no_side_effect y ) kvs 
-  | Array_append (a,b) 
   | String_append (a,b)
   | Seq (a,b) -> no_side_effect a && no_side_effect b 
   | Length (e, _)
@@ -70170,15 +70045,8 @@ let rec no_side_effect_expression_desc (x : J.expression_desc)  =
   | Bin (op, a, b) -> 
     op <> Eq && no_side_effect a && no_side_effect b     
   | Math _ 
-  | Array_of_size _
   | Array_copy _ 
-  (* | Tag_ml_obj _ *)
-  | J.Anything_to_number _
   | Js_not _
-  | String_of_small_int_array _ 
-  | Json_stringify _ 
-  | Anything_to_string _ 
-  | Dump _ 
   | Cond _ 
 
   | FlatCall _ 
@@ -70239,6 +70107,8 @@ let rec eq_expression
     ({expression_desc = x0}  : J.expression) 
     ({expression_desc = y0}  : J.expression) = 
   begin match x0  with 
+    | Null -> y0 = Null
+    | Undefined -> y0 = Undefined
     | Number (Int i) -> 
       begin match y0 with  
         | Number (Int j)   -> i = j 
@@ -70299,12 +70169,6 @@ let rec eq_expression
           p0 = p1 && b0 =  b1 && eq_expression e0 e1
         |  _ -> false 
       end
-    | Dump (l0,es0) -> 
-      begin match y0 with 
-        | Dump(l1,es1) -> 
-          l0 = l1 && eq_expression_list es0 es1
-        | _ -> false     
-      end
     | Seq (a0,b0) -> 
       begin match y0 with       
         | Seq(a1,b1) -> 
@@ -70319,23 +70183,13 @@ let rec eq_expression
     | Length _ 
     | Char_of_int _
     | Char_to_int _ 
-    | Is_null_undefined_to_boolean _ 
-    | Array_of_size _
+    | Is_null_or_undefined _ 
     | Array_copy _ 
-    | Array_append _ 
     | String_append _ 
-    | Anything_to_number _ 
-
     | Typeof _ 
     | Js_not _ 
-    | String_of_small_int_array _ 
-    | Json_stringify _ 
-    | Anything_to_string _ 
-
-
     | Cond _ 
     | FlatCall  _
-    | Bind _ 
     | String_access _ 
 
     | New _ 
@@ -70965,8 +70819,6 @@ val array_length : unary_op
 
 val string_length : unary_op
 
-val string_of_small_int_array : unary_op
-
 val bytes_length :  unary_op
 
 val function_length : unary_op
@@ -70974,9 +70826,6 @@ val function_length : unary_op
 val char_of_int : unary_op
 
 val char_to_int : unary_op
-
-val array_append : binary_op
-
 val array_copy : unary_op
 val string_append : binary_op
 (**
@@ -71075,15 +70924,6 @@ val call : ?comment:string  -> info:Js_call_info.t -> t -> t list -> t
 
 val flat_call : binary_op
 
-val dump : ?comment:string -> Js_op.level -> t list -> t
-
-
-
-(** see {!https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators#Unary_plus}*)
-(* val to_number : unary_op *)
-val int_to_string : unary_op
-
-
 val new_ : ?comment:string -> J.expression -> J.expression list -> t
 
 val array : 
@@ -71134,7 +70974,7 @@ val is_caml_block : ?comment:string -> t -> t
 
 
 val tag : ?comment:string -> J.expression -> t
-val set_tag : ?comment:string -> J.expression -> J.expression -> t
+val block_set_tag : ?comment:string -> J.expression -> J.expression -> t
 
 (** Note that this is coupled with how we encode block, if we use the 
     `Object.defineProperty(..)` since the array already hold the length,
@@ -71258,10 +71098,11 @@ let var ?comment  id  : t =
 let js_global ?comment  (v : string) =
   var ?comment (Ext_ident.create_js v )
   
-let undefined  = var Ext_ident.undefined
-
-let nil = var Ext_ident.nil  
+let undefined  : t = 
+    {expression_desc = Undefined ; comment = None}
 
+let nil : t = 
+    {expression_desc = Null ; comment = None}
 let call ?comment ~info e0 args : t = 
   {expression_desc = Call(e0,args,info); comment }
 
@@ -71344,14 +71185,6 @@ let make_block ?comment tag tag_info es mutable_flag : t =
     comment 
   }    
 
-(* let uninitialized_object ?comment tag size : t = 
-  { expression_desc = Caml_uninitialized_obj(tag,size); comment } *)
-
-(* let uninitialized_array ?comment (e : t) : t  = 
-  match e.expression_desc with 
-  | Number (Int {i = 0l; _}) -> array ?comment NA []
-  | _ -> {comment; expression_desc = Array_of_size e} *)
-
 
 module L = Literals
 (* Invariant: this is relevant to how we encode string
@@ -71365,6 +71198,7 @@ let typeof ?comment (e : t) : t =
     -> str ?comment L.js_type_string
   | Array _
     -> str ?comment L.js_type_object
+  | Bool _ -> str ?comment L.js_type_boolean
   | _ -> {expression_desc = Typeof e ; comment }
 
 
@@ -71393,8 +71227,6 @@ let math ?comment v args  : t =
    Used in [string_of_int] and format "%d"
    TODO: optimize
 *)
-let int_to_string ?comment (e : t) : t = 
-  {expression_desc = Anything_to_string e ; comment}
 
 (* Attention: Shared *mutable state* is evil, 
   [Js_fun_env.empty] is a mutable state ..
@@ -71619,22 +71451,10 @@ let char_to_int ?comment (v : t) : t =
   | Char_of_int v -> v 
   | _ -> {comment; expression_desc = Char_to_int v }
 
-let array_append ?comment e el : t = 
-  { comment ; expression_desc = Array_append (e, el)}
 
 let array_copy ?comment e : t = 
   { comment ; expression_desc = Array_copy e}
 
-(* Note that this return [undefined] in JS, 
-    it should be wrapped to avoid leak [undefined] into 
-    OCaml
-*)    
-let dump ?comment level el : t = 
-  {comment ; expression_desc = Dump(level,el)}
-
-(* let to_json_string ?comment e : t = 
-  { comment; expression_desc = Json_stringify e } *)
-
 let rec string_append ?comment (e : t) (el : t) : t = 
   match e.expression_desc , el.expression_desc  with 
   | Str(_,a), String_append ({expression_desc = Str(_,b)}, c) ->
@@ -71645,8 +71465,6 @@ let rec string_append ?comment (e : t) (el : t) : t =
     String_append ({expression_desc = Str(_,c)} ,d) ->
     string_append ?comment (string_append a (str (b ^ c))) d 
   | Str (_,a), Str (_,b) -> str ?comment (a ^ b)
-  | _, Anything_to_string b -> string_append ?comment e b 
-  | Anything_to_string b, _ -> string_append ?comment b el
   | _, _ -> {comment ; expression_desc = String_append(e,el)}
 
 
@@ -71690,17 +71508,17 @@ let float_mod ?comment e1 e2 : J.expression =
 *)
 let rec triple_equal ?comment (e0 : t) (e1 : t ) : t = 
   match e0.expression_desc, e1.expression_desc with
-  | Var (Id ({name = "undefined"|"null"} as id)), 
+  | (Null| Undefined), 
     (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ )
-    when Ext_ident.is_js id && no_side_effect e1 -> 
+    when  no_side_effect e1 -> 
     caml_false (* TODO: rename it as [caml_false] *)
   | 
     (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
-    | Fun _ | Array _ | Caml_block _ ),  Var (Id ({name = "undefined"|"null"; } as id))
-    when Ext_ident.is_js id && no_side_effect e0 -> 
+    | Fun _ | Array _ | Caml_block _ ),  (Null|Undefined)
+    when no_side_effect e0 -> 
     caml_false
   | Str (_,x), Str (_,y) ->  (* CF*)
     bool (Ext_string.equal x y)
@@ -71714,6 +71532,10 @@ let rec triple_equal ?comment (e0 : t) (e1 : t ) : t =
     bool (i0 = i1)      
   | Char_of_int a , Char_of_int b -> 
     triple_equal ?comment a b 
+  | Null, Undefined   
+  | Undefined, Null -> caml_false
+  | Null, Null
+  | Undefined, Undefined -> caml_true
   | _ -> 
      {expression_desc = Bin(EqEqEq, e0,e1); comment}
 
@@ -71722,14 +71544,7 @@ let bin ?comment (op : J.binop) e0 e1 : t =
   | EqEqEq -> triple_equal ?comment e0 e1
   | _ -> {expression_desc = Bin(op,e0,e1); comment}
 
-(* | (Bin (NotEqEq, e1,  *)
-(*         {expression_desc = Var (Id ({name = "undefined"; _} as id))}) *)
-(*   | Bin (NotEqEq,  *)
-(*          {expression_desc = Var (Id ({name = "undefined"; _} as id))},  *)
-(*          e1) *)
-(*   ),  *)
-(*   _ when Ext_ident.is_js id ->  *)
-(*   and_ e1 e2 *)
+
 (* TODO: Constant folding, Google Closure will do that?,
    Even if Google Clsoure can do that, we will see how it interact with other
    optimizations
@@ -71946,11 +71761,6 @@ let is_type_number ?comment (e : t) : t =
   string_equal ?comment (typeof e) (str "number")    
 
 
-let string_of_small_int_array ?comment xs : t = 
-  {expression_desc = String_of_small_int_array xs; comment}
-
-
-
 (* we are calling [Caml_primitive.primitive_name], since it's under our
    control, we should make it follow the javascript name convention, and
    call plain [dot]
@@ -72012,7 +71822,7 @@ let public_method_call meth_name obj label cache args =
 (*       [fn  ; arr NA args ]             *)
 (* ) *)
 
-let set_tag ?comment e tag : t = 
+let block_set_tag ?comment e tag : t = 
   seq {expression_desc = Caml_block_set_tag (e,tag); comment } unit 
 
 
@@ -72416,47 +72226,47 @@ let of_block ?comment ?e block : t =
             , Js_fun_env.empty 0)
     } []
 
-let is_null ?comment x = triple_equal ?comment x nil 
+let is_null ?comment (x : t) =   
+  triple_equal ?comment x nil 
 
 
 let is_undef ?comment x = triple_equal ?comment x undefined
 
 let for_sure_js_null_undefined (x : t) = 
   match x.expression_desc with 
-  | Var (Id ({name = "undefined" | "null"} as id)) 
-    -> Ext_ident.is_js id 
+  | Null | Undefined
+    -> true
   | _ -> false
   
 let is_null_undefined ?comment (x: t) : t = 
   match x.expression_desc with 
-  | Var (Id ({name = "undefined" | "null"} as id))
-    when Ext_ident.is_js id 
+  | Null | Undefined
     -> caml_true
   | Number _ | Array _ | Caml_block _ -> caml_false
-  | _ -> 
-     
+  | _ ->      
       { comment ; 
-        expression_desc = Is_null_undefined_to_boolean x 
+        expression_desc = Is_null_or_undefined x 
       }
 
 let eq_null_undefined_boolean ?comment (a : t) (b : t) = 
   match a.expression_desc, b.expression_desc with 
-  | Var (Id ({name = "null" | "undefined"} as id) ),   
+  | (Null | Undefined),   
     (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ )
-    when Ext_ident.is_js id -> 
+     -> 
     caml_false
   | (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ ), 
-      Var (Id ({name = "null" | "undefined"} as id) )
-    when Ext_ident.is_js id -> 
+      (Null | Undefined)
+     -> 
     caml_false
-  | Var (Id ({name = "null" | "undefined" as n1 } as id1) ), 
-    Var (Id ({name = "null" | "undefined" as n2 } as id2) )
-    when Ext_ident.is_js id1 && Ext_ident.is_js id2 
-   ->  bool (n1 = n2)    
+  | (Null, Undefined)
+  | (Undefined, Null) -> caml_false
+  | (Null, Null)
+  | (Undefined, Undefined)
+    -> caml_true
   | _ ->       
        {expression_desc = Bin(EqEqEq, a, b); comment}
     
@@ -72464,23 +72274,24 @@ let eq_null_undefined_boolean ?comment (a : t) (b : t) =
 
 let neq_null_undefined_boolean ?comment (a : t) (b : t) = 
   match a.expression_desc, b.expression_desc with 
-  | Var (Id ({name = "null" | "undefined"} as id) ),   
+  | (Null | Undefined),   
     (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ )
-    when Ext_ident.is_js id -> 
+     -> 
     caml_true
   | (Char_of_int _ | Char_to_int _ 
     | Bool _ | Number _ | Typeof _
     | Fun _ | Array _ | Caml_block _ ), 
-      Var (Id ({name = "null" | "undefined"} as id) )
-    when Ext_ident.is_js id -> 
+      (Null | Undefined)
+     -> 
     caml_true
-  | Var (Id ({name = "null" | "undefined" as n1 } as id1) ), 
-    Var (Id ({name = "null" | "undefined" as n2 } as id2) )
-    when Ext_ident.is_js id1 && Ext_ident.is_js id2 
-    ->   
-    if  n1 <> n2 then caml_true else caml_false
+  | (Null , Null )
+  | (Undefined, Undefined)
+   -> caml_false
+  | (Null, Undefined)
+  | (Undefined, Null)
+   -> caml_true
   | _ ->       
        {expression_desc = Bin(NotEqEq, a, b); comment}
 
@@ -72647,8 +72458,6 @@ let primitive ppf (prim : Lam.primitive) = match prim with
   (* | Pcreate_exception s -> fprintf ppf "[exn-create]%S" s  *)
   | Pcreate_extension s -> fprintf ppf "[ext-create]%S" s 
   | Pwrap_exn -> fprintf ppf "#exn"
-  | Pjs_string_of_small_array -> fprintf ppf "#string_of_small_array"
-  (* | Pjs_is_instance_array -> fprintf ppf "#is_instance_array" *)
   | Pcaml_obj_length -> fprintf ppf "#obj_length"
   | Pcaml_obj_set_length -> fprintf ppf "#obj_set_length"
   | Pinit_mod -> fprintf ppf "init_mod!"
@@ -73614,11 +73423,7 @@ let rec if_ ?comment  ?declaration ?else_ (e : J.expression) (then_ : J.block)
     | Bin (Bor , {expression_desc = Number (Int { i = 0l ; _})}, a), _, _ 
       -> 
       aux ?comment a  then_ else_ acc
-    (* | Bin (NotEqEq, e1,  *)
-    (*        {expression_desc = Var (Id ({name = "undefined"; _} as id))}), *)
-    (*   _, _ *)
-    (*   when Ext_ident.is_js id ->  *)
-    (*   aux ?comment e1 then_ else_ acc  *)
+
 
     | ((Bin (Gt, 
              ({expression_desc = 
@@ -83757,6 +83562,7 @@ let bind = "bind"
 let math = "Math"
 let apply = "apply"
 let null = "null"
+let undefined = "undefined"
 let string_cap = "String"
 let fromCharcode = "fromCharCode"
 let eq = "="
@@ -84646,6 +84452,11 @@ and expression l cxt  f (exp : J.expression) : Ext_pp_scope.t =
 and
   expression_desc cxt (l:int) f x : Ext_pp_scope.t  =
   match x with
+  | Null ->
+    P.string f L.null; cxt 
+  | Undefined 
+    -> 
+    P.string f L.undefined; cxt 
   | Var v ->
     vident cxt f v
   | Bool b ->
@@ -84701,16 +84512,7 @@ and
     in
     if l > 15 then P.paren_group f 1 action
     else action ()
-  | Bind (a,b) ->
-    (* a.bind(b)
-       {[ fun b -> a.bind(b) ==? a.bind ]}
-    *)
-    begin
-      expression_desc cxt l f
-        (Call ({expression_desc = Dot(a,L.bind, true); comment = None }, [b],
-               {arity = Full; call_info = Call_na}))
-    end
-
+  
   | FlatCall(e,el) ->
     P.group f 1 (fun _ ->
         let cxt = expression 15 cxt f e in
@@ -84723,34 +84525,6 @@ and
             expression 1 cxt f el
           )
       )
-  | String_of_small_int_array ({expression_desc = desc } as e) ->
-    let action () =
-      P.group f 1 (fun _ ->
-          P.string f L.string_cap;
-          P.string f L.dot ;
-          P.string f L.fromCharcode;
-          begin match desc with
-            | Array (el, _mutable)
-              ->
-              P.paren_group f 1 (fun _ -> arguments cxt f el)
-            | _ ->
-              P.string f L.dot ;
-              P.string f L.apply;
-              P.paren_group f 1 (fun _ ->
-                  P.string f L.null;
-                  P.string f L.comma;
-                  expression 1 cxt  f e  )
-          end )
-    in
-    if l > 15 then P.paren_group f 1 action
-    else action ()
-
-
-  | Array_append (e, el) ->
-    P.group f 1 (fun _ ->
-        let cxt = expression 15 cxt f e in
-        P.string f ".concat";
-        P.paren_group f 1 (fun _ -> arguments cxt f [el]))
 
   | Array_copy e ->
     P.group f 1 (fun _ ->
@@ -84759,27 +84533,6 @@ and
         P.string f "()" ;
         cxt
       )
-
-  | Dump (level, el) ->
-    let obj =
-      match level with
-      | Log -> "log"
-      | Info -> "info"
-      | Warn -> "warn"
-      | Error -> "error" in
-    P.group f 1 (fun _ ->
-        P.string f L.console;
-        P.string f L.dot;
-        P.string f obj ;
-        P.paren_group f 1 (fun _ -> arguments cxt f el))
-  | Json_stringify e
-    ->
-    P.group f 1 (fun _ ->
-        P.string f L.json ;
-        P.string f L.dot;
-        P.string f L.stringify;
-        P.paren_group f 1 (fun _ -> expression 0 cxt f e )
-      )
   | Char_to_int e ->
     begin match e.expression_desc with
       | String_access (a,b) ->
@@ -84865,20 +84618,7 @@ and
       else action ()
     );
     cxt
-  | J.Anything_to_number e
-    ->
-    let action () =
-      P.group f 0 @@ fun _ ->
-      P.string f "+" ;
-      expression 13 cxt f e
-    in
-    (* need to tweak precedence carefully
-       here [++x --> +(+x)]
-    *)
-    if l > 12
-    then P.paren_group f 1 action
-    else action ()
-  | Is_null_undefined_to_boolean e ->
+  | Is_null_or_undefined e ->
     let action = (fun _ ->
         let cxt = expression 1 cxt f e in
         P.space f ;
@@ -85016,11 +84756,6 @@ and
         P.space f ;
         expression 13 cxt  f delta
     end
-  | Anything_to_string e ->
-    (* Note that we should not apply any smart construtor here,
-       it's purely  a convenice for pretty-printing
-    *)
-    expression_desc cxt l f (Bin (Plus, E.empty_string_literal , e))
 
   | Bin (Minus, {expression_desc = Number (Int {i=0l;_} | Float {f = "0."})}, e)
     (* TODO:
@@ -85154,16 +84889,6 @@ and
     in
     if l > 15 then P.paren_group f 1 action else action ()
 
-  | Array_of_size e ->
-    let action () =
-      P.group f 1 @@ fun _ ->
-      P.string f L.new_;
-      P.space f;
-      P.string f L.array;
-      P.paren_group f 1 @@ fun _ -> expression 0 cxt f e
-    in
-    if l > 15 then P.paren_group f 1 action else action ()
-
   | Cond (e, e1, e2) ->
     let action () =
       (* P.group f 1 @@ fun _ ->  *)
@@ -85344,39 +85069,33 @@ and statement_desc top cxt f (s : J.statement_desc) : Ext_pp_scope.t =
       | Caml_block_set_tag _
       | Length _
       | Caml_block_set_length _
-      | Anything_to_string _
-      | String_of_small_int_array _
       | Call _
-      | Array_append _
       | Array_copy _
       | Caml_block_tag _
       | Seq _
       | Dot _
       | Cond _
       | Bin _
-      | Is_null_undefined_to_boolean _
+      | Is_null_or_undefined _
       | String_access _
       | Access _
-      | Array_of_size _
       | String_append _
       | Char_of_int _
       | Char_to_int _
-      | Dump _
-      | Json_stringify _
       | Math _
       | Var _
+      | Undefined
+      | Null
       | Str _
       | Unicode _
       | Array _
       | Caml_block  _
       | FlatCall _
       | Typeof _
-      | Bind _
       | Number _
       | Js_not _
       | Bool _
       | New _
-      | J.Anything_to_number _
         -> false
       (* e = function(x){...}(x);  is good
       *)
@@ -86690,7 +86409,6 @@ let rec no_side_effects (lam : Lam.t) : bool =
       (* | Pjs_is_instance_array *)
       | Pwrap_exn
         -> true
-      | Pjs_string_of_small_array
       | Pcaml_obj_set_length        
       | Pjs_apply
       | Pjs_runtime_apply
@@ -87071,7 +86789,7 @@ and eq_primitive ( lhs : Lam.primitive) (rhs : Lam.primitive) =
   | Pupdate_mod -> rhs = Pupdate_mod
   | Pbswap16 -> rhs = Pbswap16
   | Pjs_function_length -> rhs = Pjs_function_length
-  | Pjs_string_of_small_array -> rhs = Pjs_string_of_small_array
+  (* | Pjs_string_of_small_array -> rhs = Pjs_string_of_small_array *)
   (* | Pjs_is_instance_array -> rhs = Pjs_is_instance_array *)
   | Pcaml_obj_length -> rhs = Pcaml_obj_length
   | Pcaml_obj_set_length -> rhs = Pcaml_obj_set_length
@@ -88383,54 +88101,11 @@ class virtual map =
        ]}       
      *)
                  (** where we use a trick [== null ] *)
-                 (* used in [#create_array] primitive, note having
-       uninitilized array is not as bad as in ocaml, 
-       since GC does not rely on it
-     *)
-                 (* shallow copy, like [x.slice] *)
-                 (* For [caml_array_append]*)
-                 (* | Tag_ml_obj of expression *) (* js true/false*)
+                 (* shallow copy, like [x.slice] *) (* js true/false*)
                  (* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence 
      [typeof] is an operator     
   *)
-                 (* !v *) (* String.fromCharCode.apply(null, args) *)
-                 (* Convert JS boolean into OCaml boolean 
-       like [+true], note this ast talks using js
-       terminnology unless explicity stated                       
-     *)
-                 (* TODO: in the future, it might make sense to group primitivie by type,
-     which makes optimizations easier
-     {[ JSON.stringify(value, replacer[, space]) ]}
-  *)
-                 (* for debugging utitlites, 
-     TODO:  [Dump] is not necessary with this primitive 
-     Note that the semantics is slightly different from [JSON.stringify]     
-     {[
-       JSON.stringify("x")       
-     ]}
-     {[
-       ""x""       
-     ]}     
-     {[
-       JSON.stringify(undefined)       
-     ]}     
-     {[
-       undefined       
-     ]}
-     {[ '' + undefined
-     ]}     
-     {[ 'undefined'
-     ]}     
-  *)
-                 (* TODO: 
-     add 
-     {[ Assert of bool * expression ]}     
-  *)
-                 (* to support 
-       val log1 : 'a -> unit
-       val log2 : 'a -> 'b -> unit 
-       val log3 : 'a -> 'b -> 'c -> unit 
-     *)
+                 (* !v *)
                  (* TODO: Add some primitives so that [js inliner] can do a better job *)
                  (* [int_op] will guarantee return [int32] bits 
      https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators  *)
@@ -88440,10 +88115,6 @@ class virtual map =
        if it's know at compile time, we can turn it into
        f(args[0], args[1], ... )
      *)
-                 (* {[ Bind (a,b) ]}
-     is literally
-     {[ a.bind(b) ]}
-  *)
                  (* Analysze over J expression is hard since, 
         some primitive  call is translated 
         into a plain call, it's better to keep them
@@ -88636,30 +88307,15 @@ class virtual map =
           let _x_i1 = o#length_object _x_i1 in Length (_x, _x_i1)
       | Char_of_int _x -> let _x = o#expression _x in Char_of_int _x
       | Char_to_int _x -> let _x = o#expression _x in Char_to_int _x
-      | Is_null_undefined_to_boolean _x ->
-          let _x = o#expression _x in Is_null_undefined_to_boolean _x
-      | Array_of_size _x -> let _x = o#expression _x in Array_of_size _x
+      | Is_null_or_undefined _x ->
+          let _x = o#expression _x in Is_null_or_undefined _x
       | Array_copy _x -> let _x = o#expression _x in Array_copy _x
-      | Array_append (_x, _x_i1) ->
-          let _x = o#expression _x in
-          let _x_i1 = o#expression _x_i1 in Array_append (_x, _x_i1)
       | String_append (_x, _x_i1) ->
           let _x = o#expression _x in
           let _x_i1 = o#expression _x_i1 in String_append (_x, _x_i1)
-      | Anything_to_number _x ->
-          let _x = o#expression _x in Anything_to_number _x
       | Bool _x -> let _x = o#bool _x in Bool _x
       | Typeof _x -> let _x = o#expression _x in Typeof _x
       | Js_not _x -> let _x = o#expression _x in Js_not _x
-      | String_of_small_int_array _x ->
-          let _x = o#expression _x in String_of_small_int_array _x
-      | Json_stringify _x -> let _x = o#expression _x in Json_stringify _x
-      | Anything_to_string _x ->
-          let _x = o#expression _x in Anything_to_string _x
-      | Dump (_x, _x_i1) ->
-          let _x = o#unknown _x in
-          let _x_i1 = o#list (fun o -> o#expression) _x_i1
-          in Dump (_x, _x_i1)
       | Seq (_x, _x_i1) ->
           let _x = o#expression _x in
           let _x_i1 = o#expression _x_i1 in Seq (_x, _x_i1)
@@ -88674,9 +88330,6 @@ class virtual map =
       | FlatCall (_x, _x_i1) ->
           let _x = o#expression _x in
           let _x_i1 = o#expression _x_i1 in FlatCall (_x, _x_i1)
-      | Bind (_x, _x_i1) ->
-          let _x = o#expression _x in
-          let _x_i1 = o#expression _x_i1 in Bind (_x, _x_i1)
       | Call (_x, _x_i1, _x_i2) ->
           let _x = o#expression _x in
           let _x_i1 = o#list (fun o -> o#expression) _x_i1 in
@@ -88726,6 +88379,8 @@ class virtual map =
           let _x_i1 = o#expression _x_i1 in Caml_block_set_length (_x, _x_i1)
       | Number _x -> let _x = o#number _x in Number _x
       | Object _x -> let _x = o#property_map _x in Object _x
+      | Undefined -> Undefined
+      | Null -> Null
     method expression : expression -> expression =
       fun { expression_desc = _x; comment = _x_i1 } ->
         let _x = o#expression_desc _x in
@@ -89907,7 +89562,7 @@ let subst name export_set stats  =
             (* Mark a function as dead means it will never be scanned, 
                here we inline the function
             *)
-            Ext_list.append block @@ self#block rest
+            Ext_list.append block (self#block rest)
           | (None | Some _) ->
             self#statement st :: self#block rest
         end
@@ -89922,11 +89577,10 @@ let subst name export_set stats  =
 
 
 let tailcall_inline (program : J.program) = 
-  let _stats = get_stats program in
-  let _export_set = program.export_set in
-  program
-  |> (subst program.name _export_set _stats )# program
-  (* |> pass_beta #program *)
+  let stats = get_stats program in
+  let export_set = program.export_set in
+  (subst program.name export_set stats )#program program
+
     
 
 end
@@ -93462,7 +93116,7 @@ let translate_arg_cst (cst : External_arg_spec.cst) =
      E.int (Int32.of_int i)
    | Arg_string_lit i -> 
      E.str i
-   | Arg_js_null  -> E.raw_js_code Exp "null"
+   | Arg_js_null  -> E.nil
    | Arg_js_json s 
      -> E.raw_js_code Exp s
 
@@ -94121,12 +93775,8 @@ let translate_ffi
        2. support [@@bs.scope "window"]
        we need know whether we should call [add_js_module] or not 
     *)
-    begin match name, handle_external_opt external_module_name , scopes with 
-      | "null", None, [] -> E.nil 
-      | "undefined", None, [] -> E.undefined
-      | _, _, _ -> 
-        translate_scoped_module_val external_module_name name scopes
-    end
+      translate_scoped_module_val external_module_name name scopes
+
   | Js_send {splice  = js_splice ; name ; pipe = false; js_send_scopes = scopes } -> 
     begin match args  with
       | self :: args -> 
@@ -95059,13 +94709,6 @@ let translate loc (prim_name : string)
     | "caml_power_float"  -> 
       E.math "pow" args
 
-
-    | "caml_array_append" -> 
-      begin match args with 
-        | [e0;e1] -> E.array_append e0 e1
-        | _ ->  assert false 
-      end
-
     | "caml_array_get" -> 
       call Js_runtime_modules.array
     | "caml_array_get_addr"
@@ -95580,8 +95223,6 @@ let translate loc (prim_name : string)
             *)
             | _ -> E.array_copy a
           end
-        (* if Js_analyzer.is_constant a then a
-           else E.array_copy a *)
         | _ -> assert false 
       end
     | "caml_obj_block" -> 
@@ -95615,20 +95256,11 @@ let translate loc (prim_name : string)
     | "caml_nativeint_of_string" 
     | "caml_int64_format"
     | "caml_int64_of_string"
+    | "caml_format_int" 
       -> 
       call Js_runtime_modules.format 
-    | "caml_format_int" -> 
-      begin match args with 
-        | [ {expression_desc = Str (_, "%d"); _}; v] 
-          ->
-          E.int_to_string v 
-        | _ -> 
-          call Js_runtime_modules.format
-      end
     (*   "caml_alloc_dummy"; *)
     (* TODO:   "caml_alloc_dummy_float"; *)
-
-
     | "caml_obj_is_block"
       -> 
       begin match args with 
@@ -95685,7 +95317,7 @@ let translate loc (prim_name : string)
       call Js_runtime_modules.obj_runtime
     | "caml_obj_set_tag" 
       -> begin match args with 
-          | [a;b]  -> E.set_tag a b 
+          | [a;b]  -> E.block_set_tag a b 
           | _ -> assert false end
     | "caml_obj_tag" -> 
       (* Note that in ocaml, [int] has tag [1000] and [string] has tag [252]
@@ -95932,8 +95564,8 @@ let translate  loc
     begin match args with 
       | [e] -> 
         begin match e.expression_desc with 
-          | Var _ -> 
-            E.econd (E.is_null e) Js_of_lam_option.none (Js_of_lam_option.some e)
+          | Var _ | Undefined | Null -> 
+            E.econd (E.is_null e) Js_of_lam_option.none (Js_of_lam_option.some e)           
           | _ ->
             E.runtime_call Js_runtime_modules.js_primitive
               "null_to_opt" args 
@@ -95950,7 +95582,7 @@ let translate  loc
     begin match args with 
       | [e] -> 
         begin match e.expression_desc with 
-          | Var _ -> 
+          | Var _ | Undefined | Null -> 
             E.econd (E.is_undef e) Js_of_lam_option.none (Js_of_lam_option.some e)
           | _ -> 
             E.runtime_call Js_runtime_modules.js_primitive  
@@ -95968,7 +95600,7 @@ let translate  loc
     begin match args with 
       | [e] -> 
         begin match e.expression_desc with 
-          | Var _ -> 
+          | Var _ | Undefined | Null   -> 
             E.econd (E.is_null_undefined e) 
               Js_of_lam_option.none 
               (Js_of_lam_option.some e)
@@ -95994,18 +95626,6 @@ let translate  loc
       | [a;b] -> E.set_length a b 
       | _ -> assert false 
     end
-  | Lam.Pjs_string_of_small_array -> 
-    begin match args with 
-      | [e] -> E.string_of_small_int_array e 
-      | _ -> assert false 
-    end 
-  (* | Lam.Pjs_is_instance_array -> 
-    begin match args with 
-      | [e] -> E.is_instance_array e 
-      | _ -> assert false 
-    end  *)
-
-
   | Pis_null -> 
     begin match args with 
       | [e] -> E.is_null e 
@@ -96560,9 +96180,7 @@ let translate  loc
   (*   assert false (\* already handled *\) *)
   (* assert false *)
   | Pduprecord ((Record_regular 
-                | Record_float ),0)
-  | Pduprecord ((Record_regular 
-                | Record_float ),_) -> 
+                | Record_float ),_size) -> (* _size is the length of all_lables*)
     begin match args with 
       | [e] -> Js_of_lam_record.copy e
       | _ -> assert false