效果预览按下右侧的“点击预览”按钮可以在当前页面预览,点击链接可以全屏预览。https://codepen.io/comehope/pen/rqyoYY可交互视频此视频是可以交互的,你可以随时暂停视频,编辑视频中的代码。请用 chrome, safari, edge 打开观看。https://scrimba.com/p/pEgDAM/c6p2Es2源代码下载每日前端实战系列的全部源代码请从 github 下载:https://github.com/comehope/front-end-daily-challenges代码解读定义 dom,容器中包含一个名为 .emoji 的子容器,代表一个头像,它的子元素 eye left、eye right、mouth 分别代表左眼、右眼和嘴巴:<section class=“container”> <div class=“emoji”> <span class=“eye left”></span> <span class=“eye right”></span> <span class=“mouth”></span> </div></section>居中显示:body { margin: 0; height: 100vh; display: flex; align-items: center; justify-content: center; background-color: lightyellow;}定义容器尺寸和子元素对齐方式:.container { position: relative; width: 20em; height: 20em; font-size: 10px; display: flex; align-items: center; justify-content: center;}定义头像的轮廓:.emoji { position: relative; box-sizing: border-box; width: 10em; height: 10em; background-color: pink; border-radius: 50% 50% 75% 50%;}定义头像眼睛的轮廓:.emoji .eye { position: absolute; box-sizing: border-box; width: 3em; height: 3em; border: 0.1em solid gray; border-radius: 50%; top: 3em;}.emoji .eye.left { left: 1em;}.emoji .eye.right { right: 1em;}画出眼珠:.emoji .eye.left::before,.emoji .eye.right::before { content: ‘’; position: absolute; width: 1em; height: 1em; background-color: #222; border-radius: 50%; top: 1em; left: calc((100% - 1em) / 2);}画出微笑的嘴:.emoji .mouth { position: absolute; width: 2em; height: 2em; border: 0.1em solid; bottom: 1em; left: 40%; border-radius: 50%; border-color: transparent gray gray transparent; transform: rotate(20deg);}接下来制作眼珠转向 4 个方向的效果。用 2 个变量分别表示眼珠的定位位置:.emoji .eye { –top: 1em; –left: calc((100% - 1em) / 2);}.emoji .eye.left::before,.emoji .eye.right::before { top: var(–top); left: var(–left);}设置眼珠在 4 个方向的定位位置:.emoji.top .eye { –top: 0;}.emoji.bottom .eye { –top: 1.8em;}.emoji.left .eye { –left: 0;}.emoji.right .eye { –left: 1.8em;}此时,如果为 dom 元素 .emoji 增加 top、bottom、left、right 4 个样式中的任何一个样式,眼珠就会转向特定的方向。在 dom 中增加 4 个元素,每个元素的内容是一个 @ 字符:<section class=“container”> <div class=“emoji”> <!– 略 –> </div> <span class=“tip top”>@</span> <span class=“tip left”>@</span> <span class=“tip right”>@</span> <span class=“tip bottom”>@</span></section>把 4 个元素布局在头像周围:.tip { position: absolute; cursor: pointer; font-size: 4.5em; color: silver; font-family: sans-serif; font-weight: 100;}.tip.top { top: -15%;}.tip.bottom { bottom: -15%;}.tip.left { left: -15%;}.tip.right { right: -15%;}写一段脚本,增加一点交互效果。当鼠标悬停在 4 个方向的 @ 上时,使眼珠朝相应的方向转去。这里的 DIRECTION 常量存储了 4 个方向,EVENTS 常量存储了 2 个鼠标事件,$ 常量包装了根据类名获取 dom 元素的操作:const DIRECTIONS = [’top’, ‘bottom’, ’left’, ‘right’]const EVENTS = [‘mouseover’, ‘mouseout’]const $ = (className) => document.getElementsByClassName(className)[0]DIRECTIONS.forEach(direction => EVENTS.forEach((e) => $(tip ${direction}
).addEventListener(e, () => $(’emoji’).classList.toggle(direction) ) ))为眼珠设置缓动时间,使动画平滑:.emoji .eye.left::before,.emoji .eye.right::before { transition: 0.3s;}接下来制作 tooltip 提示框。为 4 个 @ 符号的 dom 增加 data-tip 属性,其内容就是 tooltip 信息:<section class=“container”> <div class=“emoji”> <!– 略 –> </div> <span class=“tip top” data-tip=“look up”>@</span> <span class=“tip bottom” data-tip=“look down”>@</span> <span class=“tip left” data-tip=“look to the left”>@</span> <span class=“tip right” data-tip=“look to the right”>@</span></section>用 ::before 伪元素展示提示信息,样式为黑底白字:.tip::before { content: attr(data-tip); position: absolute; font-size: 0.3em; font-family: sans-serif; width: 10em; text-align: center; background-color: #222; color: white; padding: 0.5em; border-radius: 0.2em; box-shadow: 0 0.1em 0.3em rgba(0, 0, 0, 0.3);}把顶部的提示框定位到顶部 @ 符号的上方正中:.tip.top::before { top: 0; left: 50%; transform: translate(-50%, calc(-100% - 0.6em));}类似地,把其他 3 个提示框也定位到 @ 符号的旁边:.tip.bottom::before { bottom: 0; left: 50%; transform: translate(-50%, calc(100% + 0.6em));}.tip.left::before { left: 0; top: 50%; transform: translate(calc(-100% - 0.6em), -50%);}.tip.right::before { right: 0; top: 50%; transform: translate(calc(100% + 0.6em), -50%);}用 ::after 伪元素在顶部提示框下面画出一个倒三角形:.tip::after { content: ‘’; position: absolute; font-size: 0.3em; width: 0; height: 0; color: #222; border: 0.6em solid transparent;}.tip.top::after { border-bottom-width: 0; border-top-color: currentColor; top: -0.6em; left: 50%; transform: translate(-50%, 0);}类似地,在其他 3 个提示框旁边画出三角形:.tip.bottom::after { border-top-width: 0; border-bottom-color: currentColor; bottom: -0.6em; left: 50%; transform: translate(-50%, 0);}.tip.left::after { border-right-width: 0; border-left-color: currentColor; left: -0.6em; top: 50%; transform: translate(0, -50%);}.tip.right::after { border-left-width: 0; border-right-color: currentColor; right: -0.6em; top: 50%; transform: translate(0, -50%);}最后,隐藏提示框,使提示框只在鼠标悬停时出现:.tip::before,.tip::after { visibility: hidden; filter: opacity(0); transition: 0.3s;}.tip:hover::before,.tip:hover::after { visibility: visible; filter: opacity(1);}大功告成!