Esvisit NPM | npm.io

Esvisit

Esvisit is a simple npm module for visiting JavaScript abstract syntax trees that are compatible with Mozilla parser API as described in https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Parser_API#Programs. This module supports exclusvely ECMAScript5 as described in http://www.ecma-international.org/ecma-262/5.1/. Benefits of using Esvisit includes:

Process iteratively and avoid recursion.
Get an alternative type that better reflects JavaScript semantic.
Visit only actual statements and expressions.

Demonstration

var Esvisit = require('esvisit');
var Esprima = require('esprima');

function indent () { return (new Array(depth+1)).join("  ") }
function visitStatement (type, stmt) { visit('Statement', type, stmt) }
function visitExpression (type, expr) { visit('Expression', type, expr) }
function visit (kind, type, node) {
  var id = ++counter;
  console.log(indent()+'Begin'+kind+id+': '+type+'('+Esvisit.ExtractInformation(type, node).join(", ")+')')
  depth++
  push(function () {
    depth--
    console.log(indent()+'End'+id)
  })
}

var code = 'o.a = eval("2*"+x);' // Your JS code here...
var ast = Esprima.parse(code)
var counter = 0;
var depth = 0;
var push = Esvisit.Prepare(visitStatement, visitExpression)

push(ast)

Output:

BeginStatement1: Expression()
  BeginExpression2: MemberAssignment(a, =)
    BeginExpression3: EvalCall(1)
      BeginExpression4: Binary(+)
        BeginExpression5: Literal(2*)
        End5
        BeginExpression6: Identifier(x)
        End6
      End4
    End3
    BeginExpression7: Identifier(o)
    End7
  End2
End1

API

This module exposes four functions:

Prepare(StatementCallback, ExpressionCallBack): prepare upcoming visits ; returns a function to push something on the worker list. Callbacks are called with: the Esvisit type of the current node and the current node itself. Esvisit types are described in the sections 'Statement Types' and 'Expression Types'
ExtractInformation(EsvisitType, Node)
ExtractStatementInformation(EsvisitType, Statement)
ExtractExpressionInformation(EsvisitType, Expression)

Statement Types

Type	Interpretation	Information
`Empty`	alias for `EmptyStatement`	`[]`
`Strict`	`'use strict';`	[]
`Block`	*	`[Length]`
`Expression`	*	`[]`
`If`	*	`[HasAlternate]`
`Label`	*	`[Label]`
`Break`	*	`[MaybeLabel]`
`Continue`	*	`[MaybeLabel]`
`With`	*	`[]`
`Switch`	*	`[Cases::[IsDefault, Length]]`
`Return`	*	`[HasValue]`
`Throw`	*	`[]`
`Try`	*	`[BodyLength, MaybeCatchParameter, MaybeCatchLength, MaybeFinalizerLength]`
`While`	*	`[]`
`DoWhile`	*	`[]`
`DeclarationFor`	`for (VAR_DECL; EXPR; EXPR) STMT`	`[Declarators::[Name, HasInit], HasTest, HasUpdate]`
`For`	`for (EXPR; EXPR; EXPR) STMT`	`[HasInit, HasTest, HasUpdate]`
`IdentifierForIn`	`for (ID in EXPR) STMT`	`[Name]`
`MemberForIn`	`for (MEMBER in EXPR) STMT`	`[MaybeProperty]`
`DeclarationForIn`	`for (var ID [=EXPR] in EXPR) STMT`	`[Name, HasInit]`
`Definition`	alias for `FunctionDeclaration`	`[Name, Parameters::[Name], BodyLength]`
`Declaration`	alias for `VariableDeclaration`	`[Declarators::[Name, HasInit]]`

(*): Add Statement to the type to obtain the Mozilla alias.

Expression Types

Type	Interpretation	Information
`This`	alias for `ThisExpression`	`[]`
`Array`	**	`[Elements::[IsInitialized]]`
`Object`	**	`[Properties::[KeyValue, Kind, MaybeParameter, MaybeBodyLength]]`
`Function`	**	`[MaybeName, Parameters::[Name], BodyLength]`
`Sequence`	**	`[Length]`
`IdentifierTypeof`	`typeof ID`	`[Name]`
`IdentifierDelete`	`delete ID`	`[Name]`
`MemberDelete`	`delete MEMBER`	`[MaybeProperty]`
`Unary`	**	`[Operator]`
`Binary`	**	`[Operator]`
`IdentifierAssignment`	`ID ASS_OP EXPR`	`[Name, Operator]`
`MemberAssignment`	`MEMBER ASS_OP EXPR`	`[MaybeProperty, Operator]`
`IdentifierUpdate`	`++ID`, `--ID`, `ID++`, `ID--`	`[IsPrefix, Operator, Name]`
`MemberUpdate`	`++MEMBER`, `--MEMBER`, `MEMBER++`, `MEMBER--`	`[IsPrefix, Operator, MaybeProperty]`
`Logical`	**	`[Operator]`
`Conditional`	**	`[]`
`New`	**	`[ArgumentsLength]`
`MemberCall`	`MEMBER(EXPRS)`	`[MaybeProperty, ArgumentsLength]`
`EvalCall`	`eval(EXPRS)`	`[ArgumentsLength]`
`Call`	`EXPR(EXPRS)`	`[ArgumentsLength]`
`Member`	**	`[MaybeProperty]`
`Identifier`	alias for `Identifier`	`[Name]`
`Literal`	alias for `Literal`	`[Value]`