How to isolate unsecure JavaScript code

Question

I need to isolate user-written code snippets from each other in javascript. For now the funniest thing i can think of is closures:

function executor() {
  window.alert('Hello!');
  size0 = document.getElementById("load").innerHTML;
  window.alert('zero:' +  size0);
  (function(document){
    // document = {"innerHTML":"empty"};
    window.alert('Hello again!');
    size1 = document.getElementById("load").innerHTML;
    window.alert('first:' + size1);
    (function(window){
      size2 = document.getElementById("load").innerHTML;
      window.alert('Hello now!');
      window.alert('second:' + size2);
      // window.alert('second:' +document.getElementById('load').size());
    })("empty");
  })("empty");
}

Is there a better and safer way to do this? Can i close prototype for various things like arrays?

Answer 1

As far as I know the easiest, and best, way to sandbox javascript is via iframes. Here is a blog post that might help.

Answer 2

You could look at Caja from Google. It's designed for running scripts from third parties safely and securely.