Trivial drag event registering function for jquery

on_drag.js

  function on_drag(el, handler) {
      var el = $(el);

      el.on("mousedown", function (e) { 
        var initial_x = e.clientY;
        var initial_y = e.clientY;        

        function drag_handler(e) {
          var delta_x = e.clientX - initial_x;
          var delta_y = e.clientY - initial_y;          

          handler(delta_x, delta_y);
        }        
        
        function drag_end () {
          $(window).off("mousemove", drag_handler);
          return false;    
        }

        $(window).on("mousemove", drag_handler)
                 .one("mouseup", drag_end)
                 .one("blur", drag_end);
                    
      });  
  }