用javascript 的正则表达式来验证Email地址是否格式正确！

 1// 检查 E-mail 是否已被注册
 2    function CheckExists()
 3    {
 4        var e = document.getElementById("mailaddress").value;
 5        if(e != "") {
 6            if(!/(\S)+[@]{1}(\S)+[.]{1}(\w)+/.test(e)) 
 7            {
 8                alert("请输入格式正确的 e-mail 地址！");
 9                var email = document.getElementById ( "mailaddress" );
10                email.value = "";
11                email.focus ();
12            } 
13            else 
14            {
15                QuickRegisterBox.IsEMailExists(e, CheckExists_Callback);
16            }
17        }
18    }