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Convert JavaScript objects to AST, then to code. Build new code like playing with legos.
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README.md

astify

Astify generates Abstract Syntax Trees from objects in live JS (as well as from source). Want to convert the entire global object to source? global.toAST().toSource(). Beyond adding toAST, astify also makes build AST (which is then convertable to code using toSource) super simple to do. Frankenstein different pieces of objects and functions together to make new ones.

This is still experimental and unfinished.

Usage

It is currently set up for use in Node.js (will be combining for a browser build soon).

var astify = require('astify');

astify.install(global); //the toAST functions must be explicitly installed on a global object
console.log(global.toAST().toSource()); // anything can be converted to AST

API

  • astify.install(context): Install the toAST prototype functions on a given global object, defaulting to the main global.
  • anything.toAST(showHidden, identity)_: Builtins get specialized toAST methods. showHidden includes non-enumerable properties. identity labels an object which doesn't have a discernable name. By default a gensym is provided.
  • astify.parseFile(filename): creates AST from sourcecode.
  • astify.createNode(type, args...): creates an AST Node from scratch.

Selectors

To select nodes you can use css-like syntax (work in progress) using node.find(selector). Some examples:

  • function function function var - descending selectors, this would filter to vars that are inside 3 nested functions.
  • function > id - child selector requires nodes to be direct children
  • var.declarations - select specific properties
  • function.params.id - select multiple properties
  • function:scope - select all the nodes in the current scope
  • method[kind = ""][key != "constructor"].value - selects methods (es6) with no kind (normal) where key is notEqual to constructor, then selectos its value property (a function expression).
  • method[key = "constructor"].value:first - selects the first method with the name "constructor" and returns its value (function expr)
  • ident:first-child - selects all identifiers that are first-children
  • return:last-child - select all return statements which are last children
  • call[callee = "super"] - select functions calls where the function name is "super"
  • member[object=super] - selects expressions that look like "super.prop"

Node Creation

An intro example to manually assembling nodes

var _ = astify.createNode;

// intermix explicit AST node definitions with regular functions, objects, and literals
var myAST = _('object', {
  a: 50,
  b: _('function').declare({
    somevar: 5,
    another: _('iife').append([
      _('return', _('function', 'another'))
    ])
  }),
  c: function hi(){
    return 'stuff';
  },
  get d(){ return this.b.name }
});

Which produces

console.log(myAST.toSource());
// -->
var myAST = {
  a: 50,
  b: function () {
    var somevar = 5,
        another = function () {
          return function another() {
          };
        }();
  },
  c: function hi() {
    return 'stuff';
  },
  get d() {
    return this.b.name;
  }
};

And the AST:

{ type: 'ObjectExpression',
  properties:
   [ { type: 'Property',
       key: { type: 'Identifier', name: 'a' },
       value: { type: 'Literal', value: 50 },
       kind: 'init' },
     { type: 'Property',
       key: { type: 'Identifier', name: 'b' },
       value:
        { type: 'FunctionExpression',
          params: [],
          id: null,
          body:
           { type: 'BlockStatement',
             body:
              [ { type: 'VariableDeclaration',
                  kind: 'var',
                  declarations:
                   [ { type: 'VariableDeclarator',
                       id: { type: 'Identifier', name: 'somevar' },
                       init: { type: 'Literal', value: 5 } },
                     { type: 'VariableDeclarator',
                       id: { type: 'Identifier', name: 'another' },
                       init:
                        { type: 'CallExpression',
                          callee:
                           { type: 'FunctionExpression',
                             params: [],
                             id: null,
                             body:
                              { type: 'BlockStatement',
                                body:
                                 [ { type: 'ReturnStatement',
                                     argument:
                                      { type: 'FunctionExpression',
                                        params: [],
                                        id: { type: 'Identifier', name: 'another' },
                                        body: { type: 'BlockStatement', body: [] } } } ] } },
                          arguments: [] } } ] } ] } },
       kind: 'init' },
     { type: 'Property',
       key: { type: 'Identifier', name: 'c' },
       value:
        { type: 'FunctionExpression',
          id: { type: 'Identifier', name: 'hi' },
          params: [],
          body:
           { type: 'BlockStatement',
             body:
              [ { type: 'ReturnStatement',
                  argument: { type: 'Literal', value: 'stuff' } } ] } },
       kind: 'init' },
     { type: 'Property',
       key: { type: 'Identifier', name: 'd' },
       value:
        { type: 'FunctionExpression',
          id: { type: 'Identifier', name: 'd' },
          params: [],
          body:
           { type: 'BlockStatement',
             body:
              [ { type: 'ReturnStatement',
                  argument:
                   { type: 'MemberExpression',
                     computed: false,
                     object:
                      { type: 'MemberExpression',
                        computed: false,
                        object: { type: 'Identifier', name: 'this' },
                        property: { type: 'Identifier', name: 'b' } },
                     property: { type: 'Identifier', name: 'name' } } } ] } },
       kind: 'get' } ] }

Node Types

The short name can be used to identify the when using astify.createNode. Optional arguments are in [brackets].

  • "assign" - AssignmentExpression(operator, left, right)
  • "array" - ArrayExpression([elementArray])
  • "block" - BlockStatement([bodyStatementsArray])
  • "binary" - BinaryExpression(operator, left, right)
  • "break" - BreakStatement([label])
  • "call" - CallExpression(callee, [argsExpressionsArray])
  • "catch" - CatchClause(param, [[bodyBlock])
  • "conditional" - ConditionalExpression(test, consequentExpression, alternateExpression)
  • "continue" - ContinueStatement([label])
  • "dowhile" - DoWhileStatement(test, [bodyBlock])
  • "debugger" - DebuggerStatement()
  • "empty" - EmptyStatement()
  • "expression" - ExpressionStatement(expression)
  • "for" - ForStatement([init, test, update, bodyBlock])
  • "forin" - ForInStatement(left, right, [bodyBlock])
  • "functiondecl" - FunctionDeclaration(id, [bodyBlock, params])
  • "function" - FunctionExpression([id, bodyBlock, params])
  • "identifier" - Identifier(name)
  • "if" - IfStatement(test, [consequentBlock, alternateBlock])
  • "literal" - Literal(value)
  • "labeled" - LabeledStatement(label, [bodyBlock])
  • "logical" - LogicalExpression(operator, left, right)
  • "member" - MemberExpression(object, property)
  • "new" - NewExpression(callee, [argsArray])
  • "object" - ObjectExpression([propertiesArray])
  • "program" - Program([bodyBlock, comments])
  • "property" - Property(kind, key, value)
  • "return" - ReturnStatement([argument])
  • "sequence" - SequenceExpression(expressionsArray)
  • "switch" - SwitchStatement(descriminant, [casesArray])
  • "case" - SwitchCase([test, consequent])
  • "this" - ThisExpression()
  • "throw" - ThrowStatement(argument)
  • "try" - TryStatement([block, handlers, finalizer])
  • "unary" - UnaryExpression(operator, argument)
  • "update" - UpdateExpression(operator, argument, [isPrefix])
  • "var" - VariableDeclaration(kind, [declarationsArray])
  • "decl" - VariableDeclarator(id, [init])
  • "while" - WhileStatement(test, [bodyBlock])
  • "with" - WithStatement(object, [bodyBlock])
  • "iife" - ImmediatelyInvokedFunctionExpression([func, argsArray])
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