<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>title</title> </head> <body> <!-- 请您输入邮箱地址:<input type="text" value="" id="email"/> *<br/> --> 请您输入邮箱地址:<input type="text" value="" id="email" /> *<br /> <script> //若是输入的是邮箱,那么背景颜色为绿色,不然为红色 //获取文本框,注册失去焦点的事件 document.getElementById("email").onblur = function () { //判断这个文本框中输入的是否是邮箱 var reg = /^[0-9a-zA-Z_.-]+[@][0-9a-zA-Z_.-]+([.][a-zA-Z]+){1,2}$/; if (reg.test(this.value)) { this.style.backgroundColor = "green"; } else { this.style.backgroundColor = "red"; } }; </script> </body> </html>