title: adding custom functions into Array.prototype
body: <p>I was working on an AJAX-enabled asp.net application.
  I've just added some methods to Array.prototype like</p>
  
  <pre><code>Array.prototype.doSomething = function(){
     ...
  }
  </code></pre>
  
  <p>This solution worked for me, being possible reuse code in a 'pretty' way.</p>
  
  <p>But when I've tested it working with the entire page, I had problems..
  We had some custom ajax extenders, and they started to behave as the unexpected: some controls displayed 'undefined' around its content or value.</p>
  
  <p>What could be the cause for that? Am I missing something about modifing the prototype of standart objects?</p>
  
  <p>Note: I'm pretty sure that the error begins when I modify the prototype for Array. It should be only compatible with IE.</p>