title: event.clientX and event.clientY vs event.x and event.y
body: <p>When detecting mouse x and y coordinates, is it best to use event.clientX and event.clientY like this:</p>
  
  <pre><code>function show_coords(event){
    var x=event.clientX;
    var y=event.clientY;
    alert("X coords: " + x + ", Y coords: " + y);
  }
  </code></pre>
  
  <p>or use x and y, like this:</p>
  
  <pre><code>function show_coords(event){
    var x=event.x;
    var y=event.y;
    alert("X coords: " + x + ", Y coords: " + y);
  }
  </code></pre>
  
  <p>Is one method better/faster than the other? They seem to work identically to me.</p>