title: Changing the value of "this"
body: <p>I have this function :</p>
  
  <pre><code>Number.prototype.f=function()
  {
      this=2;//This is not working
  }
  var x=0;
  x.f();
  alert(a);//Here I want that x equal 2
  </code></pre>
  
  <p>And I want that x is 2 at the end!</p>