有趣的交互系列 - 文字遮罩入场效果

在这个系列里分享一些简单，但是很有意思的交互效果~
附上demo地址和github地址

滚动，添加对应加载的class(比如loaded)

1. 巧用animation实现文字和遮罩层的动画效果
2. 文字动画: opacity 0 -> 1;
3. 遮罩层动画: 首先width 0 -> 100%,然后把width 100% -> 0且left 0 -> 100%，这样就实现了遮罩层的进场和退出效果;

html:

<div class="main">
    <ul class="inner">
        <li>
            <p data-js="reveal">SANDWICHES&nbsp;&amp;&nbsp;PANCAKE</p>
            <p data-js="reveal">GARDEN</p>
            <p data-js="reveal">MORNING&nbsp;&amp;&nbsp;TOMORROW&nbsp;&amp;&nbsp;FRIEND</p>
            <p data-js="reveal">
                ORANGE&nbsp;&amp;&nbsp;BIRD&nbsp;&amp;&nbsp;SHEEP&nbsp;&amp;&nbsp;CUP&nbsp;&amp;&nbsp;BUS</p>
            <p data-js="reveal">APPLE&nbsp;&amp;&nbsp;FRUIT&nbsp;&amp;&nbsp;CAR</p>
            <p data-js="reveal">CAKE&nbsp;&amp;&nbsp;PICTURE&nbsp;&amp;&nbsp;CAT&nbsp;&amp;&nbsp;STAMP</p>
            <p data-js="reveal">
                PLANE&nbsp;&amp;&nbsp;BOOK&nbsp;&amp;&nbsp;RACKET&nbsp;&amp;&nbsp;GLASS&nbsp;&amp;&nbsp;BED</p>
        </li>
        <li>
            <p data-js="reveal">APPLE<br>BANANA&nbsp;&amp;&nbsp;PINE APPLE&nbsp;&amp;&nbsp;SHEEP</p>
            <p data-js="reveal">BANANA&nbsp;&amp;&nbsp;PINE APPLE</p>
        </li>
        <li>
            <p data-js="reveal">PUMPKIN&nbsp;&amp;&nbsp;TARO&nbsp;&amp;&nbsp;CARROT</p>
        </li>
        <li>
            <p data-js="reveal">HORSERADISH&nbsp;&amp;&nbsp;LETTUCE</p>
            <p data-js="reveal">PUMPKIN&nbsp;&amp;&nbsp;TARO&nbsp;&amp;&nbsp;CARROT</p>
            <p data-js="reveal">HORSERADISH&nbsp;&amp;&nbsp;LETTUCE</p>
            <p data-js="reveal">POTATO&nbsp;&amp;&nbsp;BURDOCK</p>
        </li>
        <li>
            <p data-js="reveal">
                EGG&nbsp;&amp;&nbsp;BAG&nbsp;&amp;&nbsp;ROSE&nbsp;&amp;&nbsp;CHAIR&nbsp;&amp;&nbsp;BAT</p>
            <p data-js="reveal">
                FISH&nbsp;&amp;&nbsp;NOTEBOOK&nbsp;&amp;&nbsp;PENCIL&nbsp;&amp;&nbsp;DOG&nbsp;&amp;&nbsp;DESK</p>
            <p data-js="reveal">WATCH&nbsp;&amp;&nbsp;MITT&nbsp;&amp;&nbsp;MILK&nbsp;&amp;&nbsp;FLOWER</p>
            <p data-js="reveal">DOOR&nbsp;&amp;&nbsp;BOAT&nbsp;&amp;&nbsp;PIANO&nbsp;&amp;&nbsp;</p>
        </li>
        <li>
            <p data-js="reveal">POTATO&nbsp;&amp;&nbsp;BURDOCK</p>
            <p data-js="reveal">APPLE<br>BANANA&nbsp;&amp;&nbsp;PINE APPLE</p>
            <p data-js="reveal">LETTER<br>CAP&nbsp;&amp;&nbsp;TAPE&nbsp;&amp;&nbsp;MAIL&nbsp;&amp;&nbsp;BOX</p>
        </li>
        <li>
            <p data-js="reveal">APPLE<br>BANANA&nbsp;&amp;&nbsp;PINE APPLE</p>
            <p data-js="reveal">TURNIP&nbsp;&amp;&nbsp;OKRA&nbsp;&amp;&nbsp;PEA</p>
        </li>
        <li>
            <p data-js="reveal">SHIITAKE&nbsp;&amp;&nbsp;BEEFSTEAK PLANT</p>
        </li>
    </ul>
</div>

css:

body {
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    background-color: #000;
}

main {
    padding: 10vw 0;
}

ul {
    width: 100%;
    max-width: 70%;
    margin: 0 auto;
}

li {
    margin: 10vw 0;
    text-align: left;
}

p {
    display: block;
    color: #fff;
    font-family: 'Lato', sans-serif;
    font-size: 2vw;
    font-weight: 900;
    line-height: 1.2;
}

p+p {
    margin-top: 10px;
}

li:first-child {
    margin-top: 0;
}

li:last-child {
    margin-bottom: 0;
}

li:nth-child(even) {
    text-align: right;
}

a {
    color: #fff;
}

a:hover {
    text-decoration: none;
}

[data-reveal="content"] {
    display: inline-block;
    position: relative;
}

[data-reveal="cover"] {
    position: absolute;
    top: 0;
    left: 0;
    width: 0;
    height: 100%;
    z-index: 1;
}

[data-reveal="text"] {
    opacity: 0;
}

@keyframes reveal-cover {
    0% {
        width: 0;
        left: 0;
    }

    44% {
        width: 100%;
        left: 0;
    }

    54% {
        width: 100%;
        left: 0;
    }

    100% {
        width: 0;
        left: 100%;
    }
}

@keyframes reveal-text {
    0% {
        opacity: 0;
    }

    44% {
        opacity: 0;
    }

    54% {
        opacity: 1;
    }
}

[data-js="reveal"].loaded [data-reveal="cover"] {
    animation: reveal-cover 1.5s ease-in-out;
}

[data-js="reveal"].loaded [data-reveal="text"] {
    opacity: 1;
    animation: reveal-text 1.5s ease-in-out;
}

javascript:

const COLOR_LIST = ['#7f00ff', '#ff00ff', '#0000ff', '#007fff', '#00ffff'];
let $targetList;

const init = () => {

    $targetList = document.querySelectorAll('[data-js="reveal"]');

    setup();

    window.addEventListener('scroll', onScroll, false);
    window.dispatchEvent(new Event('scroll'));
}

// 随机获取数组项
const getArrayRandomValue = (array) => array[Math.floor(Math.random() * array.length)];

const setup = () => {
    for (const $target of $targetList) {
        const content = $target.innerHTML;
        const color = 'revealColor' in $target.dataset ? $target.dataset.revealColor : getArrayRandomValue(COLOR_LIST);
        $target.innerHTML = `<span data-reveal="content"><div data-reveal="cover" style="background-color:${color}"></div><span data-reveal="text">${content}</span></span>`;
    }
}

const onScroll = () => {
    const windowH = window.innerHeight;
    const scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
    const isMostScroll = document.body.clientHeight <= scrollTop + windowH;

    for (const $target of $targetList) {

        if ($target.classList.contains('loaded')) continue;

        const rect = $target.getBoundingClientRect();
        const top = rect.top + scrollTop;
        if (isMostScroll || top <= scrollTop + (windowH * .8)) $target.classList.add('loaded');

    }

}
document.addEventListener('DOMContentLoaded', init, false);