What underlies this JavaScript idiom: var self = this?
<p>I saw the following in the source for <a href="http://webkit.org/misc/DatabaseExample.html">WebKit HTML 5 SQL Storage Notes Demo</a>:    </p>

<pre><code>function Note() {
  var self = this;

  var note = document.createElement('div');
  note.className = 'note';
  note.addEventListener('mousedown', function(e) { return self.onMouseDown(e) }, false);
  note.addEventListener('click', function() { return self.onNoteClick() }, false);
  this.note = note;
  // ...
}
</code></pre>

<p>The author uses <em>self</em> in some places (the function body) and <em>this</em> in other places (the bodies of functions defined in the argument list of methods).  What's going on?  Now that I've noticed it once, will I start seeing it everywhere?</p>
