JS实现鼠标按下拖拽效果

原生JS实现鼠标按下拖拽效果

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>鼠标拖动</title>
    <style type="text/css">body {
            margin: 0;
        }

        div {
            width: 200px;
            height: 200px;
            position: absolute;
            background-color: pink;
        }</style>
</head>

<body>

    <div onmousedown="downDiv(this)" onmousemove="moveDiv(this)" onmouseup="upDiv(this)">

    </div>



    <script>//定义变量储存div的宽高
        var obj_w, obj_h;
        //定义一个变量判断是否执行移动函数
        var mouseDown = false;

        //鼠标按下函数
        function downDiv(obj) {
            //获取div的宽高
            obj_w = obj.offsetWidth;
            obj_h = obj.offsetHeight;
            //鼠标
            var e = event || window.event;
            //e.clientX/Y 是获取鼠标相对浏览器的位置;将div中心自动居中到鼠标
            obj.style.left = (e.clientX - obj_w / 2) + "px";
            obj.style.top = (e.clientY - obj_h / 2) + "px";
            console.log(obj.style.left, obj.style.top)
            //按下时为ture,松开时为false,以判断是否执行执行mouveDiv
            mouseDown = true;

        }

        //鼠标移动函数
        function moveDiv(obj) {
            obj_w = obj.offsetWidth;
            obj_h = obj.offsetHeight;
            var e = event || window.event;
            console.log(e.clientX, e.clientY);
            console.log(obj_w, obj_h);
            if (mouseDown) {
                obj.style.left = (e.clientX - obj_w / 2) + "px";
                obj.style.top = (e.clientY - obj_h / 2) + "px";
                console.log(obj.style.left, obj.style.top)
            }

        }

        //鼠标松开函数
        function upDiv(obj) {
            mouseDown = false;
        }</script>
</body>

</html>
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我是有底线的