Question

How would I go about writing a lightweight javascript to javascript parser. Something simple that can convert some snippets of code.

I would like to basically make the internal scope objects in functions public.

So something like this

var outer = 42;
window.addEventListener('load', function() {
   var inner = 42;
   function magic() {
       var in_magic = inner + outer;
       console.log(in_magic);
   }
   magic();
}, false);

Would compile to

__Scope__.set('outer', 42);
__Scope__.set('console', console);
window.addEventListener('load', constructScopeWrapper(__Scope__, function(__Scope__) {
    __Scope__.set('inner', 42);
    __Scope__.set('magic',constructScopeWrapper(__Scope__, function _magic(__Scope__) {
        __Scope__.set('in_magic', __Scope__.get('inner') + __Scope__.get('outer'));
        __Scope__.get('console').log(__Scope__.get('in_magic'));
    }));
    __Scope__.get('magic')();
}), false);

Demonstation Example

Motivation behind this is to serialize the state of functions and closures and keep them synchronized across different machines (client, server, multiple servers). For this I would need a representation of [[Scope]]

Questions:

1. Can I do this kind of compiler without writing a full JavaScript -> (slightly different) JavaScript compiler?
2. How would I go about writing such a compiler?
3. Can I re-use existing js -> js compilers?

Answer 1

If you want something with a simple interface, you could try node-burrito: https://github.com/substack/node-burrito

It generates an AST using the uglify-js parser and then recursively walks the nodes. All you have to do is give a single callback which tests each node. You can alter the ones you need to change, and it outputs the resulting code.