H总结

<style type="text/css">
            *{
                margin: 0;
                padding: 0;
            }
            div{
                width: 200px;
                height: 200px;
            }
            #div1{
                background-color: lightpink;
                position: absolute;
                top: 100px;
                left: 100px;
                /*默认都是0，这个值大的在上面，小的在下面*/
                /*z-index: 1;*/  
            }
            #div2{
                background-color: lightgreen;
                position: absolute;
                top: 150px;
                left: 150px;
                /*z-index: 2;*/
                
            }
            #div3{
                background-color: cornflowerblue;
                position: absolute;
                top: 20px;
                left: 200px;
            }
            
        </style>
    </head>
    <body>
        <div id="div1"></div>
        <div id="div2"></div>
        <div id="div3"></div>
        <script type="text/javascript">
            var div1Node = document.getElementById('div1');
            div1Node.style.left = '100px';
            div1Node.style.top = '100px';
            var div2Node = document.getElementById('div2');
            div2Node.style.left = '150px';
            div2Node.style.top = '150px';
            var div3Node = document.getElementById('div3');
            div3Node.style.left = '20px';
            div3Node.style.top = '200px';
            var divNodeArray = document.getElementsByTagName('div')
            //保存最上层的标签的z-index的值
            var maxZ = 0;
            var offsetX1, offsetY1;
            //修改层次(鼠标按下)
            function clickAction(evt){
                maxZ++;
                this.style.zIndex = maxZ;
                this.isDown = true;
                offsetX1 = evt.offsetX;
                offsetY1 = evt.offsetY;
            }
            
            //移动事件驱动程序
            function dragAction(evt){
                //按住不放的时候移动
                if(this.isDown){
                    var left = parseInt(this.style.left.slice(0,-2));
                    var top = parseInt(this.style.top.slice(0,-2));
                    this.style.left = (left+(evt.offsetX-offsetX1))+'px';
                    this.style.top = (top+(evt.offsetY-offsetY1))+'px';
                }
            }
            //绑定事件
            for(x in divNodeArray){
                var divNode = divNodeArray[x];
                //绑定按下事件
                divNode.onmousedown = clickAction;
                divNode.onmousemove = dragAction;
                divNode.onmouseup = function(){
                    this.isDown = false;
                }
                divNode.onmouseleave = function(){
                    this.isDown = false;
                }
            }
            
            
            
            
        </script>
···
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