Drag 'n' Drop: JavaScript

function beginDrag(e) { 
  dump("drag start\n"); 
  window.lastX=e.clientX; 
  window.lastY=e.clientY; 
  window.onmousemove=doDrag; 
  window.onmouseup=endDrag; 
} 

function endDrag(e) { 
  dump("drag end\n"); 
  window.onmousemove=null; 
}