https://github.com/mishoo/UglifyJS
gives access to an ast in javascript.
ast.coffee
util = require 'util'
jsp = require('uglify-js').parser
orig_code = """
var a = function (x) {
return x * x;
};
function b (x) {
return a(x)
}
console.log(a(5));
console.log(b(5));
"""
ast = jsp.parse(orig_code)
console.log util.inspect ast, true, null, true