27. js - Throttling Case 2: Use throttling to control page scrolling frequency

<!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>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        header {
            width: 100%;
            height: 40px;
            background: pink;
        }

        main {
            width: 100%;
            height: 4500px;
            background: cadetblue;
            position: relative;
        }

        .wrap-box {
            position: fixed;
            top: 40%;
            right: 0;
            background: rgb(226, 168, 75);
        }

        .wrap-box p {
            padding: 20px;
            border-bottom: 1px solid #ccc;
        }

        .active {
            color: red;
        }
    </style>
</head>

<body>
    <header>header</header>
    <main>
        <div class="wrap-box">
            <p>ts</p>
            <p>pinia</p>
            <p>vite</p>
        </div>
        <section style="height: 1500px; background: #4066bf;">ts</section>
        <section style="height: 1500px; background: #9aae44;">pinia</section>
        <section style="height: 1500px; background: #ce3db6;">vite</section>
    </main>
</body>

</html>
<script src="./lodash.min.js"></script>
<script>
    // 保证资源家在完毕，高度已经撑开
    window.onload = () => {
        document.addEventListener('scroll', _.throttle(function () {
            // 获取文档滚动高度
            let top = document.documentElement.scrollTop;
            const nodeList = document.querySelectorAll('p');
            nodeList.forEach(item => {
                item.classList.remove('active');
                if (top < 1540) {
                    nodeList[0].classList.add('active');
                } else if (top >= 1540 && top < 3040) {
                    nodeList[1].classList.add('active');
                } else if (top >= 3040) {
                    nodeList[2].classList.add('active');
                }
            })
        }, 1000));
    }


</script>
27. js - Throttling Case 2: Use throttling to control page scrolling frequency

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