页面LOADING效果

<!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>
        body {
            font-family: monospace;
        }

        .overlay {
            position: absolute;
            bottom: 0;
            left: 0;
             100%;
            height: 30vh;
            z-index: 100;
            background: white;
            background: linear-gradient(0deg, white 75%, rgba(255, 255, 255, 0.9) 80%, rgba(255, 255, 255, 0.25) 95%, rgba(255, 255, 255, 0) 100%);
        }

        .text {
            font-size: 100px;
            display: flex;
            position: absolute;
            bottom: 20vh;
            left: 50%;
            transform: translateX(-50%);
            user-select: none;
        }

        .text .wrapper {
            padding-left: 20px;
            padding-right: 20px;
            padding-top: 20px;
        }

        .text .wrapper .letter {
            transition: ease-out 1s;
            transform: translateY(10%);
        }

        .text .wrapper .shadow {
            transform: scale(1, -1);
            color: #999;
            transition: ease-in 5s, ease-out 5s;
        }

        /* .text .wrapper:hover .letter {
            transform: translateY(-200%);
        }

        .text .wrapper:hover .shadow {
            opacity: 0;
            transform: translateY(200%);
        } */
    </style>
</head>

<body>
    <div class="overlay"></div>
    <div class="text"></div>
</body>

<script>

    var str = 'LOADING',
        arr = [],
        html = '';

    for (let i = 0; i < str.length; i++) {
        const val = str[i];
        arr.push(i)

        html += `<div class="wrapper">
                    <div id="letter-${i}" class="letter">${val}</div>
                    <div id='shadow-${i}' class="shadow">${val}</div>
                </div>`;
    }
    document.querySelector('.text').innerHTML = html;


    // 闭包是为了访问函数内部的变量而实现循环效果
    function Loading() {
        var index = 0;

        function changePosition(val) {
            console.log(val);

            var current_letter = document.querySelector(`#letter-${val}`);
            var current_shadow = document.querySelector(`#shadow-${val}`);

            current_letter.style.transform = 'translateY(-100%)';
            current_shadow.style.transform = 'translateY(100%)';

            setTimeout(() => {
                current_letter.style.transform = 'translateY(10%)';
                current_shadow.style.transform = 'translateY(0%)';
            }, 1000);

            setTimeout(() => {
                index += 1;
                if (index >= arr.length) {
                    index = 0;
                }
                changePosition(arr[index]);
            }, 500);
        }
        return changePosition;
    }

    setTimeout(() => {
        Loading()(arr[0])
    }, 500);
</script>

</html>
页面LOADING效果

CSS参考于：https://codepen.io/kajetan-orski/pen/YzQObKg
