what's the line meaning in javascript
<pre><code>function bind( obj, type, fn ) {
    if ( obj.attachEvent ) {
        obj['e'+type+fn] = fn;
        obj[type+fn] = function(){obj['e'+type+fn]( window.event );}
        obj.attachEvent( 'on'+type, obj[type+fn] );
    } else
        obj.addEventListener( type, fn, false );
}
</code></pre>

<p>i am new to javascript, the above code is from the internet. i don't understand the above function well, expect someone can explain it to me. thank you, why it declare three argument(obj, type, fn).  <code>obj['e'+type+fn]</code> what's this line meaning.</p>
