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。javascript
https://codepen.io/comehope/pen/qMPQPxcss
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。html
請用 chrome, safari, edge 打開觀看。前端
https://scrimba.com/p/pEgDAM/cMGa4TQjava
每日前端實戰系列的所有源代碼請從 github 下載:git
https://github.com/comehope/front-end-daily-challengesgithub
定義 dom,容器中包含 2 個元素,分別表明 2 條軌道:chrome
<div class="container"> <span class='track'></span> <span class='track'></span> </div>
居中顯示:dom
body { margin: 0; height: 100vh; display: flex; align-items: center; justify-content: center; background-color: #999; }
定義容器尺寸和子元素的佈局方式:佈局
.container { font-size: 30px; width: calc(13em + 0.5em); height: 8em; display: flex; flex-direction: column; justify-content: space-between; }
定義 2 個色值,一個亮的和一個暗的:
.container { --dark: #222; --light: #ddd; }
畫出 2 條軌道的輪廓:
.track { width: inherit; height: 2em; border: 1px solid var(--dark); }
爲 2 條軌道的背景圖案,圖案是明暗相間的條紋,但第 2 條軌道要錯半個格:
.track { background: linear-gradient( 90deg, var(--dark) 50%, var(--light) 50% ); background-size: 1em; } .track:nth-child(2) { background-position: 0.5em; }
用僞元素畫出 2 個矩形:
.track { position: relative; display: flex; align-items: center; } .track::before { content: ''; position: absolute; width: 2em; height: 0.8em; background-color: var(--light); }
讓這 2 個矩形在軌道上往復移動:
.track::before { animation: move 5s linear infinite alternate; } @keyframes move { from { left: 0; } to { left: calc(100% - 2em); } }
此時,兩個矩形看起來是一先一後地前進的,但實際上它們是在同一時刻開始而且以相同的速度在移動。接下來咱們來揭祕真相。
在 dom 中增長一個子元素,做爲按鈕;
<div class="container"> <span class='track'></span> <span class='track'></span> <span class="toggle">Show me the truth</span> </div>
設置按鈕的樣式:
.toggle { order: -1; width: 10em; height: 2em; border: 2px solid var(--dark); border-radius: 0.2em; font-size: 0.5em; font-family: sans-serif; font-weight: bold; color: black; text-align: center; line-height: 2em; cursor: pointer; user-select: none; }
爲按鈕設置與軌道風格相似的背景,以及鼠標懸停效果:
.toggle { background-image: linear-gradient(to right, #ddd 50%, #999 50%); background-size: 1em; transition: 0.5s; } .toggle:hover { background-position: 5em; }
增長一段點擊按鈕時觸發的腳本,爲軌道元素切換樣式:
let $toggle = document.getElementsByClassName('toggle')[0] let $tracks = Array.from(document.getElementsByClassName('track')) $toggle.addEventListener('click', function() { $tracks.forEach(track => track.classList.toggle('highlights')) })
終於,謎底就在切換樣式以後被揭曉了:
.track::before { box-sizing: border-box; border: solid var(--dark); border-width: 0; } .track.highlights::before { background-color: white; border-width: 0.1em; }
大功告成!