jQuery实现类似360首页导航拖拽Div排序特效

实现拖拽的代码如下：
$(function() {
		function Pointer(x, y) {
			this.x = x ;
			this.y = y ;
		}
		function Position(left, top) {
			this.left = left ;
			this.top = top ;
		}
		$(".item_content .item").each(function(i) {
			this.init = function() { // 初始化
				this.box = $(this).parent() ;
				$(this).attr("index", i).css({
					position : "absolute",
					left : this.box.offset().left,
					top : this.box.offset().top
				}).appendTo(".item_content") ;
				this.drag() ;
			},
			this.move = function(callback) {  // 移动
				$(this).stop(true).animate({
					left : this.box.offset().left,
					top : this.box.offset().top
				}, 500, function() {
					if(callback) {
						callback.call(this) ;
					}
				}) ;
			},
			this.collisionCheck = function() {
				var currentItem = this ;
				var direction = null ;
				$(this).siblings(".item").each(function() {
					if(
						currentItem.pointer.x >this.box.offset().left &&
						currentItem.pointer.y >this.box.offset().top &&
						(currentItem.pointer.x < this.box.offset().left + this.box.width()) &&
						(currentItem.pointer.y < this.box.offset().top + this.box.height())
					) {
						// 返回对象和方向
						if(currentItem.box.offset().top < this.box.offset().top) {
							direction = "down" ;
						} else if(currentItem.box.offset().top >this.box.offset().top) {
							direction = "up" ;
						} else {
							direction = "normal" ;
						}
						this.swap(currentItem, direction) ;
					}
				}) ;
			},
			this.swap = function(currentItem, direction) { // 交换位置
				if(this.moveing) return false ;
				var directions = {
					normal : function() {
						var saveBox = this.box ;
						this.box = currentItem.box ;
						currentItem.box = saveBox ;
						this.move() ;
						$(this).attr("index", this.box.index()) ;
						$(currentItem).attr("index", currentItem.box.index()) ;
					},
					down : function() {
						// 移到上方
						var box = this.box ;
						var node = this ;
						var startIndex = currentItem.box.index() ;
						var endIndex = node.box.index(); ;
						for(var i = endIndex; i >startIndex ; i--) {
							var prevNode = $(".item_content .item[index="+ (i - 1) +"]")[0] ;
							node.box = prevNode.box ;
							$(node).attr("index", node.box.index()) ;
							node.move() ;
							node = prevNode ;
						}
						currentItem.box = box ;
						$(currentItem).attr("index", box.index()) ;
					},
					up : function() {
						// 移到上方
						var box = this.box ;
						var node = this ;
						var startIndex = node.box.index() ;
						var endIndex = currentItem.box.index(); ;
						for(var i = startIndex; i < endIndex; i++) {
							var nextNode = $(".item_content .item[index="+ (i + 1) +"]")[0] ;
							node.box = nextNode.box ;
							$(node).attr("index", node.box.index()) ;
							node.move() ;
							node = nextNode ;
						}
						currentItem.box = box ;
						$(currentItem).attr("index", box.index()) ;
					}
				}
				directions[direction].call(this) ;
			},
			this.drag = function() { // 拖拽
				var oldPosition = new Position() ;
				var oldPointer = new Pointer() ;
				var isDrag = false ;
				var currentItem = null ;
				$(this).mousedown(function(e) {
					e.preventDefault() ;
					oldPosition.left = $(this).position().left ;
					oldPosition.top =  $(this).position().top ;
					oldPointer.x = e.clientX ;
					oldPointer.y = e.clientY ;
					isDrag = true ;
					
					currentItem = this ;
					
				}) ;
				$(document).mousemove(function(e) {
					var currentPointer = new Pointer(e.clientX, e.clientY) ;
					if(!isDrag) return false ;
					$(currentItem).css({
						"opacity" : "0.8",
						"z-index" : 999
					}) ;
					var left = currentPointer.x - oldPointer.x + oldPosition.left ;
					var top = currentPointer.y - oldPointer.y + oldPosition.top ;
					$(currentItem).css({
						left : left,
						top : top
					}) ;
					currentItem.pointer = currentPointer ;
					// 开始交换位置
					
					currentItem.collisionCheck() ;
					
					
				}) ;
				$(document).mouseup(function() {
					if(!isDrag) return false ;
					isDrag = false ;
					currentItem.move(function() {
						$(this).css({
							"opacity" : "1",
							"z-index" : 0
						}) ;
					}) ;
				}) ;
			}
			this.init() ;
		}) ;
	}) ;