<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>用循环将三个DIV变成红色</title> <style> #outer{330px;height:100px;margin:10px auto;} #outer div{float:left;100px;height:100px;margin:0 5px;background:black;} </style> <script> window.onload = function () { var oDiv = document.getElementById("outer").getElementsByTagName("div"); var oBtn = document.getElementsByTagName("button")[0]; oBtn.onclick = function () { for(var i = 0; i < oDiv.length; i++) oDiv[i].style.background = "red"; } } </script> </head> <body> <center><button>点击将DIV变成红色</button></center> <div id="outer"> <div></div> <div></div> <div></div> </div> </body> </html>