JS extend functionality of a method
<p>I'm trying to extend the functionality of some methods of the 2dcontext object, however I can't get it to work the way I want: I want to override a method, but I want to call the original method from the overridden method like this:</p>

<pre><code>//First get the original context
var ctx = canvas.getContext("2d");

//Create a class which uses ctx as it's prototype
var ExtendedContext = function (){};
ExtendedContext.prototype = ctx;

//And extend a method
ExtendedContext.prototype.fillRect = function(x, y, width, height) {
    //Do some stuff
    this.prototype.fillRect(x, y, width, height); //Doesn't work
    //Do some more stuff
};
</code></pre>

<p>How can I call the original <code>fillRect</code> method from inside my own method?</p>
