检查是否输入的为email地址

function  checkInputemail(element){
   var nPointIndex = -1;
   var value = RTrim(element.value);
if(value=="")return "true";
for (var j = 0; j <  value.length; j++){
var ch = value.substr(j, 1);
if (ch == "@"){
if (nPointIndex != -1){
element.focus();
if (element.alertTitle != undefined)
alert(element.alertTitle+":输入的值只能有一个@");
else
alert("在该项输入的值只能有一个@");
return "false";
}else
nPointIndex = j;
}
}
if (nPointIndex == -1){
element.focus();
if (element.alertTitle != undefined)
alert(element.alertTitle+":输入的值不存在@");
else
alert("在该项输入的值不存在@");
return "false";
}
return "true";

}