How to approach parsing through a javascript file?

Question

I want to parse through a javascript and find all the variable declarations, attributions, and calls to functions from a specific library.

What would be the best approach:regular expressions, lexer, use something already done that does that (does it exist?)....?

What I want in fact is to be assured that an object namespace and methods are not modified, and this through a static analysis.

The browser already does this pretty well. You can use an inspector/profiler to see the result of the parsing. — Jonas G. Drange, Aug 09 '12 at 07:37

Sergey · Accepted Answer · 2012-08-09T09:14:21.880

You can not do it with regexes and probably you also do not want to write you own implementation of ecma-standard 262 (It is a total overkill).
As for me I dig google's V8 javascript engine, more precisely PyV8. I suggest you can use it.

If you had problems there is the code I used to install (pip installation had an error for my x64 system, so I used sources):

apt-get install subversion scons libboost-python-dev
svn checkout http://v8.googlecode.com/svn/trunk/ v8
svn checkout http://pyv8.googlecode.com/svn/trunk/ pyv8
cd v8
export PyV8=`pwd`
cd ../pyv8
sudo python setup.py build
sudo python setup.py install

As I remember these commands did not make errors for me. (I copypasted it but it worked)

Answer to the question itself:
More complex hello wolrd example, list some varibales of the global object:

import PyV8

class Global(PyV8.JSClass):      # define a compatible javascript class
    def hello(self):               # define a method
        print "Hello World"

    def alert(self, message): # my own alert function
        print type(message), '  ', message

    @property
    def GObject(self): return self

    def __setattr__(self, key, value):
        super(Global, self).__setattr__(key, value)
        print key, '=', value

G = Global()
ctxt = PyV8.JSContext(G)
ctxt.enter()
ctxt.eval("var a=hello; GObject.b=1.0; a();")
list_all_cmd = '''for (myKey in GObject){
alert(GObject[myKey]);
}'''
ctxt.eval(list_all_cmd)
ctxt.leave()

(In browsers you should call you global object - Window)
This code will output:

b = 1
Hello World
<class '__main__.Global'>    <__main__.Global object at 0x7f202c9159d0>
<class '_PyV8.JSFunction'>    function () { [native code] }
<type 'int'>    1
<class '_PyV8.JSFunction'>    function () { [native code] }
<class '_PyV8.JSFunction'>    function () { [native code] }
<class '_PyV8.JSFunction'>    function () { [native code] }
<class '_PyV8.JSFunction'>    function () { [native code] }
<class '_PyV8.JSFunction'>    function () { [native code] }
<class '_PyV8.JSFunction'>    function () { [native code] }
<class '_PyV8.JSFunction'>    function () { [native code] }
<class '_PyV8.JSFunction'>    function () { [native code] }

So in what format builds the output can I trace some variables in that? Can you give a link with an example on how can be used? — Eduard Florinescu, Aug 09 '12 at 08:31

score 0 · Answer 2 · edited May 23 '17 at 11:56

0

You can use Rhino from Mozilla. It is a Javascript implementation written in Java. 1.7R3 release onwards have a new AST API. The classes are available in org.mozilla.javascript.ast

If you want to do this in Javascript, please see this discussion JavaScript parser in JavaScript

Hope it helps.

edited May 23 '17 at 11:56

Community

1
1

answered Aug 09 '12 at 07:48

krishnakumarp

8,967
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I am already considering pynoceros(python rhino port), pynarcissus, and pyV8 so thanks for confirming my aproach :), also thanks for the sugestion with jslint parser maybe I can also find a jslint port for python and look there in the regular expressions. I see that it builds from code objects like `` any ideea how can I trace a variable through that? I don't know how to work effectively with it. – Eduard Florinescu Aug 09 '12 at 08:33

How to approach parsing through a javascript file?

2 Answers2

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