title: Re-define property-function in obj
body: <p>I'm facing such problem.
  I have a object from an library that generally says:</p>
  
  <pre><code>obj.childObj.doStuff({
     ....
     aProperty: function(params....){
        var xxx = this.someObj,
        e = this.someOtherObj;
  
        obj.doSomeXtraStuff();
     }
     ....
  });
  </code></pre>
  
  <p>I would like to override the <code>aProperty();</code> and then the global <code>obj</code> to make a call
  on my version, is that possibe in that config, and also it would be nice doing it without modifying the definition of the original obj? However I'm open to any suggestions.
  I was able to make <code>aProperty.prototype = function(p1,p2,...){.....};</code>
  but there was no effect, although it was saved in proto property?</p>