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dfatool.js is a data flow analyze tool for javascript code runs on node.js.

The code analyze is based on Parser API AST, which you can generated with Esprima. And Escodegen is needed for the final output code regenerate.

Live demo


npm install dfatool

Basic Usage

Use Esprima to generate AST

var ast = esprima.parse(data, {
	loc : true

Build scope for the program

var globalScope = dfatool.newGlobalScope();
dfatool.buildScope(ast, globalScope);

analyze the code


Get the variable defined in a specific scope

var variable = scope.getDefine("variableName");

Inference the variable's value in a specific position of program

var loc = {
	line : 20,
	column : 20
var value = variable.inference( scope.offsetLoc(loc) );

Inference the type(object,function,array,literal,expression)

var type = value.type

Read property of the value( support prototype chain look up)

var property = value.access("propName.propName");

If the value is an array

var elem = value.access(10);

If the value is an function, you can simulate an function call

var returnedVariable = value.execute(callExprAST, scope);


Here is a simple example to get code outline with dfatool

// Parse AST with esprima, loc must be set true
var ast = esprima.parse(code, {
	loc : true

var globalScope = dfatool.newGlobalScope();
dfatool.buildScope(ast, globalScope);


var outline = {};

// Iterate all the defined variables and inference its value
for(var name in globalScope._defines){
	var variable = globalScope._defines[name];
	var value = variable.inference();
	if( value ){
		outline[] = value.toJSON();

You can also run the test script under the tests folder


There are still many works todo like repeatment statement support

And sadly it seems doesn't work well on the minified code. Still can't find the problem.