JavaScript_grammar.lark

# Grammar is composed of definitions (named literals and named terminals) and some directives (at the end)
?start: (statement|expression)+ // a program is composed of one or more statement

?statement: print_statement ";"?
            | variable_statement ";"?
            | variable_assignment ";"?
            | logical_statement ";"?
            | if_statement
            | while_statement
            | return_statement ";"?
            | function_declaration
            | function_call ";"?
            | ternary_condition_statement

// Logical productions
?logical_statement : "(" logical_statement ")"
                  | logical_and
                  | logical_or
                  | logical_not
                  | relational  # <, >, <=, >=, ==, !=, ===, !==

?relational: expression "<" expression -> less_than
            | expression ">" expression -> greater_than
            | expression "<=" expression -> less_than_or_equal
            | expression ">=" expression -> greater_than_or_equal
            | equality  # equality with == in JS
            | strict_equality  # equality with === in JS
            | "(" relational ")"

?logical_or: logical_statement "||" logical_statement
           | "(" logical_or ")"

?logical_and: logical_statement "&&" logical_statement
            | "(" logical_and ")"

logical_not: "!" logical_statement
            | "!" "(" logical_not ")"

?equality: expression "==" expression
            | expression "!=" expression -> inequality

?strict_equality: expression "===" expression
                    | expression "!==" expression -> strict_inequality

// Arithmetic productions
additive: expression "+" expression -> add
           | expression "-" expression -> sub

multiplicative: term "*" term -> mul
               | term "/" term -> div

negative: "-" expression
         | "-" "(" negative ")"

?block: "{" statement* "}"

// input and output statements
input_statement: "prompt" "(" expression? ")" ";"?  # prompt can take whatever input you give to it
                | "prompt" "(" variable_assignment ")" ";"?
                | "prompt" "(" logical_statement ")" ";"?
                | "prompt" "(" function_call ")" ";"?
                | "prompt" "(" ternary_condition_statement ")" ";"?

print_statement: "console" "." "log" "(" expression? ")" ";"?
                | "console" "." "log" "(" variable_assignment ")" ";"?
                | "console" "." "log" "(" logical_statement ")" ";"?
                | "console" "." "log" "(" function_call ")" ";"?
                | "console" "." "log" "(" ternary_condition_statement ")" ";"?

// the ! is required to not filter keywords like let/const/var
!variable_statement: ("let"|"var") IDENTIFIER  ("=" (expression|function_call|logical_statement|ternary_condition_statement))?
                    |("let"|"var")? IDENTIFIER ("[" expression "]")? ("=" (expression|function_call|logical_statement|ternary_condition_statement))  // we can define but not assign a variable or vice versa
                    |"const" IDENTIFIER "=" (expression|function_call|logical_statement|ternary_condition_statement)

!variable_assignment: IDENTIFIER "+=" expression
                    | IDENTIFIER "-=" expression
                    | IDENTIFIER "*=" expression
                    | IDENTIFIER "/=" expression
                    | IDENTIFIER "++" // post-increment
                    | IDENTIFIER "--" // post-decrement
                    | "++" IDENTIFIER // pre-increment
                    | "--" IDENTIFIER // pre-decrement

?expression: "(" expression ")"
            | additive
            | term
            | negative

term : multiplicative
     | factor
     | "(" additive ")"
     | "(" term ")"

factor : BOOL
       | STRING
       | template_literal  // because it is just a more complex string
       | INT
       | FLOAT
       | IDENTIFIER
       | IDENTIFIER "[" expression "]" -> array_access
       | IDENTIFIER "." "length" -> array_length
       | input_statement
       | array

array: "[" [expression ("," expression)*] "]"

?template_literal: "`" (template_string_part | "${" (expression | logical_statement | ternary_condition_statement | function_call) "}")* "`"

?template_string_part: /[^$`]+/

!function_declaration : "function" IDENTIFIER "(" parameter_list? ")" block

?parameter_list: IDENTIFIER ("," IDENTIFIER)*

!function_call: IDENTIFIER "(" argument_list? ")"

?argument_list: expression ("," expression)*

!return_statement: "return" expression? ";"?

// branching production
?if_statement : "if" "(" (logical_statement | expression) ")" block ("else" (if_statement|block))?  // this way we include all the possible cases, statement can be a block or another if statement

// iteration production
?while_statement  : "while" "(" (logical_statement | expression) ")" block

// ternary condition statement
?ternary_condition_statement: (logical_statement | expression) "?" statement ":" statement

BOOL.1: "true" | "false"

STRING: "'" _STRING_INNER* "'"
        | "\"" _STRING_INNER* "\""

// comment management (ignore them)
MULTILINE_COMMENT: "/*" (/./ | "\n")* "*/"
INLINE_COMMENT: "//" /[^\n]*/
NEWLINE: "\n"

%import common.ESCAPED_STRING
%import common._STRING_INNER
%import common.CNAME -> IDENTIFIER
%import common.INT
%import common.FLOAT
%import common.WS

%ignore WS
%ignore INLINE_COMMENT
%ignore NEWLINE
%ignore MULTILINE_COMMENT