实现一个简单拖拽 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="box"></div>
</body>
</html>
<script>
    window.onload = function () {
        var box = document.getElementById('box');
        box.onmousedown = function (ev) {
            var oEvent = ev || window.event; // 兼容火狐,火狐下没有window.event
            var distanceX = oEvent.clientX - box.offsetLeft; // 鼠标到可视区左边的距离 - box到页面左边的距离
            var distanceY = oEvent.clientY - box.offsetTop;
            document.onmousemove = function (ev) {
            var oEvent = ev || window.event;
            var left = oEvent.clientX - distanceX;
            var top = oEvent.clientY - distanceY;
            if (left <= 0) {
                left = 0;
            } else if (left >= document.documentElement.clientWidth - box.offsetWidth) {
                left = document.documentElement.clientWidth - box.offsetWidth;
            }
            if (top <= 0) {
                top = 0;
            } else if (top >= document.documentElement.clientHeight - box.offsetHeight) {
                top = document.documentElement.clientHeight - box.offsetHeight;
            }
            box.style.left = left + 'px';
            box.style.top = top + 'px';
            }
            box.onmouseup = function () {
            document.onmousemove = null;
            box.onmouseup = null;
            }
        }
    }
</script>
<style>
    html, body {
        margin: 0;
        height: 100%;
    }
    #box {
        width: 100px;
        height: 100px;
        background-color: red;
        position: absolute;
        top: 100px;
        left: 100px;
    }
</style>

 

posted @ 2021-08-20 10:13  小灬壊  阅读(39)  评论(0)    收藏  举报