使li滚动到ul最上面 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style type="text/css">
        * {
            margin: 0;
            padding: 0;
        }

        body {
            margin: 0 auto;
            padding: 50px;
            background: #E2E2E2;
        }

        p {
            font-size: 15px;
            background: #797979;
            padding: 10px;
            border-radius: 5px;
            line-height: 2;
            text-align: center;
        }

        .flex-container {
            display: flex;
            flex-flow: row wrap;
            margin-top: 20px;
        }

        .flex-item {
            width: 100%;
            height: 500px;
            overflow: auto;
        }

        .flex-item li {
            list-style-type: none;
            width: 100%;
            height: 100px;
            background: #ffd200;
            margin: 5px 0;
            color: white;
            font-size: 30px;
            line-height: 100px;
            text-align: center;
        }
    </style>
</head>
<body>
    <div> 
        <p>hi, 滚动指定的li到ul的顶部</p>
        <div class="flex-container">
            <ul class="flex-item" id="ul">
                <li>1</li>
                <li>2</li>
                <li>3</li>
                <li>4</li>
                <li>5</li>
                <li>6</li>
                <li>7</li>
                <li>8</li>
                <li>9</li>
                <li>10</li>
                <li>11</li>
                <li>12</li>
                <li>13</li>
                <li>14</li>
                <li>15</li>
            </ul>
        </div>
    </div>

    <script type="text/javascript">

        function scrollToByIndex(index) {
            let parentDom = ul
            let ch = parentDom.children
            let currentLi = ch[index]
            let top = ch[0].offsetTop
            if (currentLi) {
                parentDom.scrollTop = currentLi.offsetTop - top
            }
        }

        scrollToByIndex(2)

        function getIndexFormArr(arr, num) {
            return arr.findIndex(function(item) {
                return item === num
            })
        }
    </script>
</body>
</html>

 

posted @ 2018-01-11 15:16  Sorrow.X  阅读(694)  评论(0)  编辑  收藏  举报