前端每日實戰：22# 視頻演示如何用純 CSS 創做出美麗的彩虹條紋文字

效果預覽

按下右側的「點擊預覽」按鈕能夠在當前頁面預覽，點擊連接能夠全屏預覽。

https://codepen.io/comehope/pen/ELpRxj

可交互視頻教程

此視頻是能夠交互的，你能夠隨時暫停視頻，編輯視頻中的代碼。

請用 chrome, safari, edge 打開觀看。

https://scrimba.com/c/czrWDfZ

源代碼下載

每日前端實戰系列的所有源代碼請從 github 下載：

https://github.com/comehope/front-end-daily-challenges

代碼解讀

定義 dom，容器中包含文本，而且包含4個 <span> 用於特效，<span> 的 data-text 屬性值爲與文本相同：

<p class="rainbow">
    web
    <span data-text="web"></span>
    <span data-text="web"></span>
    <span data-text="web"></span>
    <span data-text="web"></span>
</p>

居中顯示：

html, body {
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    background: black;
}

定義文本樣式：

.rainbow {
    color: white;
    font-size: 300px;
    text-transform: uppercase;
    font-family: sans-serif;
    font-weight: bold;
    line-height: 1em;
    position: relative;
}

用僞元素增長圖層，造成彩虹效果：

.rainbow span::before,
.rainbow span::after {
    content: attr(data-text);
    position: absolute;
    top: 0;
    left: 0;
    overflow: hidden;
}

.rainbow span:nth-child(1)::before {
    color: orchid;
    z-index: 1;
    height: calc(100% - 10% * 1);
}

.rainbow span:nth-child(1)::after {
    color: mediumpurple;
    z-index: 2;
    height: calc(100% - 10% * 2);
}

.rainbow span:nth-child(2)::before {
    color: deepskyblue;
    z-index: 3;
    height: calc(100% - 10% * 3);
}

.rainbow span:nth-child(2)::after {
    color: cyan;
    z-index: 4;
    height: calc(100% - 10% * 4);
}

.rainbow span:nth-child(3)::before {
    color: mediumspringgreen;
    z-index: 5;
    height: calc(100% - 10% * 5);
}

.rainbow span:nth-child(3)::after {
    color: yellow;
    z-index: 6;
    height: calc(100% - 10% * 6);
}

.rainbow span:nth-child(4)::before {
    color: gold;
    z-index: 7;
    height: calc(100% - 10% * 7);
}

.rainbow span:nth-child(4)::after {
    color: tomato;
    z-index: 8;
    height: calc(100% - 10% * 8);
}

增長動畫效果：

.rainbow span::before,
.rainbow span::after {
    animation: animate 0.8s infinite alternate;
    filter: opacity(0);
}

@keyframes animate {
    from {
        filter: opacity(0);
    }

    to {
        filter: opacity(1);
    }
}

爲圖層設置延時，加強動感：

.rainbow span:nth-child(1)::before {
    animation-delay: calc(0.8s - 0.1s * 1);
}

.rainbow span:nth-child(1)::after {
    animation-delay: calc(0.8s - 0.1s * 2);
}

.rainbow span:nth-child(2)::before {
    animation-delay: calc(0.8s - 0.1s * 3);
}

.rainbow span:nth-child(2)::after {
    animation-delay: calc(0.8s - 0.1s * 4);
}

.rainbow span:nth-child(3)::before {
    animation-delay: calc(0.8s - 0.1s * 5);
}

.rainbow span:nth-child(3)::after {
    animation-delay: calc(0.8s - 0.1s * 6);
}

.rainbow span:nth-child(4)::before {
    animation-delay: calc(0.8s - 0.1s * 7);
}

.rainbow span:nth-child(4)::after {
    animation-delay: calc(0.8s - 0.1s * 8);
}

最後，把原始文本設置爲透明色：

.rainbow {
    color: transparent;
}

大功告成！

知識點

• content https://developer.mozilla.org/en-US/docs/Web/CSS/content
• attr() https://developer.mozilla.org/en-US/docs/Web/CSS/attr
• calc() https://developer.mozilla.org/en-US/docs/Web/CSS/calc
• z-index https://developer.mozilla.org/en-US/docs/Web/CSS/z-index
• :nth-child() https://developer.mozilla.org/en-US/docs/Web/CSS/:nth-child