被记录和设置坐标的拖拽元素就是这个目标元素，但是它并不是整个部分都是拖拽的有效部分。我们在html结构中为拖拽的有效区域添加类draggable表示有效拖拽区域：
复制代码 代码如下:
<div>
<div>
拖拽的有效元素
</div>
<div>
拖拽对象
</div>
</div>
然后修改Drag方法如下：
function drag(ele) { var dragNode = (ele.querySelector(".draggable") || ele); dom.on(dragNode, "mousedown", function (event) { var dragElement = draggableConfig.dragElement = new DragElement(ele); draggableConfig.mouse.setXY(event.clientX, event.clientY); draggableConfig.dragElement .setXY(dragElement.target.style.left, dragElement.target.style.top) .setTargetCss({ "zIndex": draggableConfig.zIndex++, "position": "relative" }); }).on(dragNode, "mouseover", function () { dom.setCss(this, draggableStyle.dragging); }).on(dragNode, "mouseout", function () { dom.setCss(this, draggableStyle.defaults); }); }
主要修改的是绑定mousedown的节点变成了包含draggable类的有效元素，如果不含有draggable，则整个元素都是有效元素。
五、性能优化和总结
由于onmousemove在一直调用，会造成一些性能问题，我们可以通过setTimout来延迟绑定onmousemove事件，改进move函数如下
function move(event) { if (draggableConfig.dragElement) { var mouse = draggableConfig.mouse, dragElement = draggableConfig.dragElement; dragElement.setTargetCss({ "left": parseInt(event.clientX - mouse.x + dragElement.x) + "px", "top": parseInt(event.clientY - mouse.y + dragElement.y) + "px" }); dom.off(document, "mousemove", move); setTimeout(function () { dom.on(document, "mousemove", move); }, ); } }
总结：
整个拖拽插件的实现其实很简单，主要是要注意几点
1、实现思路：元素拖拽位置的改变就等于鼠标改变的距离，关键在于获取鼠标的变动和元素原本的坐标
2、通过setTimeout来延迟加载onmousemove事件来提供性能
六、jquery插件化
简单地将其封装成jquery插件，主要是相关的dom方法替换成jquery方法来操作
; (function ($, window, undefined) { //#region 拖拽元素类 function DragElement(node) { this.target = node; node.onselectstart = function () { //防止拖拽对象内的文字被选中 return false; } } DragElement.prototype = { constructor: DragElement, setXY: function (x, y) { this.x = parseInt(x) || ; this.y = parseInt(y) || ; return this; }, setTargetCss: function (css) { $(this.target).css(css); return this; } } //#endregion //#region 鼠标元素 function Mouse() { this.x = ; this.y = ; } Mouse.prototype.setXY = function (x, y) { this.x = parseInt(x); this.y = parseInt(y); } //#endregion //拖拽配置 var draggableConfig = { zIndex: , dragElement: null, mouse: new Mouse() }; var draggableStyle = { dragging: { cursor: "move" }, defaults: { cursor: "default" } } var $document = $(document); function drag($ele) { var $dragNode = $ele.find(".draggable"); $dragNode = $dragNode.length > ? $dragNode : $ele; $dragNode.on({ "mousedown": function (event) { var dragElement = draggableConfig.dragElement = new DragElement($ele.get()); draggableConfig.mouse.setXY(event.clientX, event.clientY); draggableConfig.dragElement .setXY(dragElement.target.style.left, dragElement.target.style.top) .setTargetCss({ "zIndex": draggableConfig.zIndex++, "position": "relative" }); }, "mouseover": function () { $(this).css(draggableStyle.dragging); }, "mouseout": function () { $(this).css(draggableStyle.defaults); } }) } function move(event) { if (draggableConfig.dragElement) { var mouse = draggableConfig.mouse, dragElement = draggableConfig.dragElement; dragElement.setTargetCss({ "left": parseInt(event.clientX - mouse.x + dragElement.x) + "px", "top": parseInt(event.clientY - mouse.y + dragElement.y) + "px" }); $document.off("mousemove", move); setTimeout(function () { $document.on("mousemove", move); }, ); } } $document.on({ "mousemove": move, "mouseup": function () { draggableConfig.dragElement = null; } }); $.fn.drag = function (options) { drag(this); } })(jQuery, window, undefined)