JavaScript example of drag and drop to a target

• Download source code - 1.6 KB

Introduction

This article is a sequel to the article I wrote earlier: Cross-browser drag and drop. In that article, I provided a JavaScript example of drag and drop. Here I would like to provide a JavaScript example of drag and drop to a target that would work in all browsers (including Safari-iPad).

This article is for those that like nuts and bolts and are not using third party libraries like jQuery. There is nothing wrong with using third party libraries – I just like more flexibility. For those that like nuts and bolts I would recommend this third party library: Redips.

Using the code

To use this script, use the SetupDragDrop JavaScript function. It will make some DIVs dragable and other DIVs drag targets based on the CSS class (Dragable or DropTarget) used. Please note that this example shows how to “capture” the element so that you don’t lose it if you move outside of the element or outside of the browser window. Here is the full JavaScript code:

var oDragTargets = [];
var oDragTarget = null;
var oDragItem = null;
var iClickOffsetX = 0;
var iClickOffsetY = 0;

function OnLoad(){
	SetupDragDrop();
}

function SetupDragDrop(){
	oDragTargets = [];
	
	var oList = document.getElementsByTagName("div");
	for(var i=0; i x && (oTarget.y + oTarget.h) > y){
			if (oDragTarget!=null && oDragTarget != oTarget.o) OnTargetOut();
			oDragTarget = oTarget.o;
			OnTargetOver();
			return;
		}
	}
	
	if (oDragTarget){
		OnTargetOut();
		oDragTarget = null;
	}
}

function TouchMove(e){
    e.preventDefault();
    var x = e.targetTouches[0].pageX - iClickOffsetX;
    var y = e.targetTouches[0].pageY - iClickOffsetY;
    oDragItem = e.targetTouches[0].target;
    HandleDragMove(x,y);
}

function DragStop(o,e){
	if (o.releaseCapture){
		o.releaseCapture();
	}else if (oDragItem){
		window.removeEventListener ("mousemove", DragMove2, true);
		window.removeEventListener ("mouseup",   DragStop2, true);
	}
	
	HandleDragStop();
}

function HandleDragStop(){
	if (oDragItem==null) return;

	if (oDragTarget){
		OnTargetOut();
		OnTargetDrop();
		oDragTarget = null;
	}
	
	oDragItem.style.zIndex = 1;
	oDragItem = null;
}

function TouchEnd(e){
	e.target.innerHTML = "TouchEnd";
	HandleDragStop();
}

function $(s){
	return document.getElementById(s);
}

function GetObjPos(obj){
	var x = 0;
	var y = 0;
	var o = obj;
	
	var w = obj.offsetWidth;
	var h = obj.offsetHeight;
	if (obj.offsetParent) {
		x = obj.offsetLeft
		y = obj.offsetTop
		while (obj = obj.offsetParent){
			x += obj.offsetLeft;
			y += obj.offsetTop;
		}
	}
	return {x:x, y:y, w:w, h:h, o:o};
}

//Drag and Drop Events
function OnTargetOver(){
	oDragTarget.style.border = "3px solid red";
}

function OnTargetOut(){
	oDragTarget.style.border = "";
}

function OnTargetDrop(){
	oDragItem.style.position="";
	oDragTarget.appendChild(oDragItem);
	if (navigator.platform=="iPad") MakeDragable(oDragItem);
}

I created two CSS classes to make drag-able elements not selectable and to have the cursor suggest that the element is drag-able.

.Dragable{
    cursor:move;
   -moz-user-select: -moz-none;   
   -khtml-user-select: none;   
   -webkit-user-select: none;   
   -o-user-select: none;   
   user-select: none;
   width: 100px; 
   height:20px; 
   padding: 3px;
}

.DropTarget{
    width: 200px; 
    height:200px; 
    background-color: LightBlue;
    border: 3px solid white;
}

I hope someone might find this example useful.