拖拽模版

对ctrl+a后拖动的问题做了处理
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="../reset.css">
    <style>
        .box{
            width: 100px;
            height: 100px;
            background-color: red;
            position: absolute;
            left: 0;
            top: 0;
        }
    </style>
</head>
<body>
<div class="box">111</div>

<script>
    window.onload = function () {
        var box = document.querySelector(".box");
        var boxStart = {
            left: 0,
            top: 0
        };
        var mouseStart = {
            left: 0,
            top: 0
        };
        box.onmousedown = function (ev) {
            // 绑定全局捕获
            box.setCapture && box.setCapture();
            ev = ev || window.event;
            // 阻止默认事件兼容性写法
            ev.preventDefault?ev.preventDefault():ev.returnValue=false;
            // 阻止传播兼容性写法
            // ev.stopPropagation?ev.stopPropagation():ev.cancelBubble=true;
            // 鼠标开始的位置
            mouseStart.left = ev.clientX;
            mouseStart.top = ev.clientY;

            // 盒子开始的位置
            boxStart.left = box.offsetLeft;
            boxStart.top = box.offsetTop;

            document.onmousemove = function (ev) {
                ev = ev || window.event;
                // 鼠标结束的位置
                var mouseEnd = {};
                mouseEnd.left = ev.clientX;
                mouseEnd.top = ev.clientY;

                // 移动的差值
                var mouseLenX = mouseEnd.left - mouseStart.left;
                var mouseLenY = mouseEnd.top - mouseStart.top;

                // 移动后的位置
                var L = boxStart.left + mouseLenX;
                var T = boxStart.top + mouseLenY;

                // 视口尺寸
                var winW = document.documentElement.clientWidth;
                var winH = document.documentElement.clientHeight;

                // 盒子尺寸
                var boxW = box.offsetWidth;
                var boxH = box.offsetHeight;

                L = L<0?0:L;
                L = L>=winW-boxW?winW-boxW:L;
                T = T<0?0:T;
                T = T>=winH-boxH?winH-boxH:T;

                box.style.left = L + "px";
                box.style.top = T + "px";
            };
            document.onmouseup = function () {
                // 释放全局捕获
                document.releaseCapture && document.releaseCapture();
                document.onmousemove = document.onmouseup = null;
            }
        }
    }
</script>
</body>
</html>