div边框拖拽改变宽度-蒲公英云

css盒子如下图：

注意：

刚开始测试效果不是很好，原因行内块元素之间有缝隙

消除行内块元素左右之间的间隙:给父元素设置为弹性布局flex

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box {
            width: 90%;
            height: 90vh;
            border: solid 1px black;
            display: flex; /*消除行内块元素左右之间的间隙:给父元素设置为弹性布局*/
        }
        .left {
            width: 49%;
            height: 100%;
            background: lightgrey;
            float: left;
        }
        .resize {
            width: 2%;
            height: 100%;
            background-color: orange;
            cursor: w-resize;
            float: left;
        }
        .right {
            width: 49%;
            height: 100%;
            background: lightgrey;
            float: left;
        }
    </style>
</head>
<body>
<div>
    <div class="box" id="box">
        <div class="left" id="left">左边</div>
        <div class="resize" id="resize"></div>
        <div class="right" id="right">右边</div>
    </div>
</div>
<script>
    window.onload = function () {
        let box = document.getElementById('box');
        let left = document.getElementById('left');
        let resize = document.getElementById('resize');
        let right = document.getElementById('right');
        let w = box.offsetWidth;//获取 div 元素的宽度，包含内边距（padding）和边框（border）
        let rw = resize.offsetWidth;//获取 div 元素的宽度，包含内边距（padding）和边框（border）
        //按下鼠标事件
        resize.onmousedown = function (e) {
            let startX = e.clientX;//鼠标指针的水平坐标
            resize.left = resize.offsetLeft;//分割线节点元素的左边界的偏移值
            // 鼠标拖动事件
            document.onmousemove = function (e) {
                let change = e.clientX - startX;//鼠标移动的偏移值
                let moveLen = resize.left + change;//鼠标移动后，分割线节点元素的左边界的偏移值
                resize.style.left = moveLen;
                left.style.width = moveLen + 'px';
                right.style.width = (w - moveLen - rw) + 'px';// 容器宽度 - 左边区域的宽度 - 分割线的宽度 = 右边区域的宽度
            }
            // 鼠标松开事件
            document.onmouseup = function (evt) {
                evt.stopPropagation();
                document.onmousemove = null;
                document.onmouseup = null;
                //当你不在需要继续获得鼠标消息就要应该调用ReleaseCapture()释放掉
                resize.releaseCapture && resize.releaseCapture();
            }
            //该函数在属于当前线程的指定窗口里设置鼠标捕获
            resize.setCapture && resize.setCapture();
            //对于上面出现的setCapture()和releaseCapture()的用法。必须成对出现。
        }
    }
</script>
</body>
</html>

jquey方式

注意：鼠标按下才开始记录坐标值。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="http://libs.baidu.com/jquery/1.9.1/jquery.min.js"></script>
    <style>
        body {
            padding: 20px;
        }
        th, td {
            width: 100px;
        }
        .drag-1 {
            display: inline-block;
            border-left: 3px solid red;
            height: 25px;
            position: fixed;
            left: 130px;
            cursor: w-resize;
        }
        .drag-2 {
            display: inline-block;
            border-left: 3px solid red;
            height: 25px;
            position: absolute;
            left: 233px;
            cursor: w-resize;
        }
    </style>
</head>
<body>
<div>
    <div class="drag-1"></div>
    <div class="drag-2"></div>
    <table border="1" style="border-collapse: collapse;">
        <thead>
        <tr>
            <th class="col-1">表头1</th>
            <th class="col-2">表头2</th>
            <th class="col-3">表头3</th>
        </tr>
        </thead>
        <tbody>
        <tr>
            <td class="col-1">数据1</td>
            <td class="col-2">数据2</td>
            <td class="col-3">数据3</td>
        </tr>
        <tr>
            <td class="col-1">数据1</td>
            <td class="col-2">数据2</td>
            <td class="col-3">数据3</td>
        </tr>
        </tbody>
    </table>
</div>
<script>
    $(function () {
        drag1();
        drag2();
    });
    function drag1() {
        let resize = document.getElementsByClassName('drag-1')[0];
        //按下鼠标事件
        resize.onmousedown = function (e) {
            let startX = e.clientX;//鼠标指针的水平坐标
            let drag_1 = $('.drag-1').offset().left;
            let drag_2 = $('.drag-2').offset().left;
            let col_1 = $('.col-1').width();
            // 鼠标拖动事件
            document.onmousemove = function (e) {
                let change = e.clientX - startX;//鼠标移动的偏移值
                $('.drag-1').offset({'left': drag_1 + change})
                $('.drag-2').offset({'left': drag_2 + change})
                $('.col-1').width(col_1 + change);
            }
            // 鼠标松开事件
            document.onmouseup = function (evt) {
                evt.stopPropagation();
                document.onmousemove = null;
                document.onmouseup = null;
                //当你不在需要继续获得鼠标消息就要应该调用ReleaseCapture()释放掉
                resize.releaseCapture && resize.releaseCapture();
            }
            //该函数在属于当前线程的指定窗口里设置鼠标捕获
            resize.setCapture && resize.setCapture();
            //对于上面出现的setCapture()和releaseCapture()的用法。必须成对出现。
        }
    }
    function drag2() {
        let resize = document.getElementsByClassName('drag-2')[0];
        //按下鼠标事件
        resize.onmousedown = function (e) {
            let startX = e.clientX;//鼠标指针的水平坐标
            let drag_2 = $('.drag-2').offset().left;
            let col_2 = $('.col-2').width();
            // 鼠标拖动事件
            document.onmousemove = function (e) {
                let change = e.clientX - startX;//鼠标移动的偏移值
                $('.drag-2').offset({'left': drag_2 + change})
                $('.col-2').width(col_2 + change);
            }
            // 鼠标松开事件
            document.onmouseup = function (evt) {
                evt.stopPropagation();
                document.onmousemove = null;
                document.onmouseup = null;
                //当你不在需要继续获得鼠标消息就要应该调用ReleaseCapture()释放掉
                resize.releaseCapture && resize.releaseCapture();
            }
            //该函数在属于当前线程的指定窗口里设置鼠标捕获
            resize.setCapture && resize.setCapture();
            //对于上面出现的setCapture()和releaseCapture()的用法。必须成对出现。
        }
    }
</script>
</body>
</html>