<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <style> .box{width: 200px;height: 200px;background: yellowgreen} .page{color: red} .btn{font-size: 20px;} </style> </head> <body> <div class="box">这是测试</div> <script> var box=document.getElementsByClassName("box")[0]; box.className=box.className+" "+"page";//增加类名 box.classList.add("btn");//增加类名 box.classList.remove("btn");//移除类名 box.classList.item(1);//根据索引找类名 console.log(box.className); console.log(box.classList.item(1)) </script> </body> </html>
