<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title></title> <style type="text/css"> .cls { background-color: black; } </style> </head> <body class="cls"> <input type="button" value="开/关灯" id="btn"> <script type="text/javascript"> function my$(id) { return document.getElementById(id); } my$("btn").onclick=function(){ //获取body标签 document.body.className=document.body.className!="cls"?"cls":""; } </script> </body> </html>
原文：https://www.cnblogs.com/zhangDY/p/11424203.html