~~~ <input type="text" id="email"> <script> /* 6-12数字@qq.com 395775347@qq.com /^ $/ ^-->以什么开头 $-->以什么结尾 严格匹配时,头尾必须加 */ var reg =/^\d{6,12}@qq\.com$/; var email = document.getElementById("email"); email.onchange = function(){ var value = this.value; if(!reg.test(value)){ alert("邮箱不合法") } } </script> ~~~