本篇会放置多种下划线滑动效果，一篇一篇增加，更新中
1、当前 tab 出现下划线的同时，前一个下划线同时消失（出现方向与消失方向保持一致），伴随过渡效果。
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>change tab</title> <style> ul { display: flex; position: absolute; width: 800px; top: 50%; left: 50%; transform: translate(-50%, -50%); list-style: none; } li { position: relative; padding: 20px; color: #000; line-height: 1; transition: 0.2s all linear; cursor: pointer; } li::before { content: ""; position: absolute; top: 0; left: 100%; width: 0; height: 100%; border-bottom: 2px solid #f00; transition: 0.2s all linear; } li:active { background: #000; color: #fff; } .active ~ li::before { left: 0; } .active::before { width: 100%; left: 0; top: 0; } .hover::before{ width: 200%; } </style> </head> <body> <ul> <li data-index='0'> 张杰 </li> <li data-index='1'>周杰伦</li> <li data-index='2'>林俊杰</li> <li data-index='3'>薛之谦</li> <li data-index='4'>你</li> </ul> </body> <script> var lis = document.getElementsByClassName('tab'); for(var i=0; i<lis.length; i++){ lis[i].onclick = function(){ var that = this; for(var i=0; i<lis.length; i++){ lis[i].classList.remove('active') this.classList.add('active') } } } </script> </html>