자바스크립트 이메일 체크 함수

function _check_email(email) {
var pattern = /^(.+)@(.+)$/;
var atom = "\[^\\s\\(\\)<>#@,;:!\\\\\\\"\\.\\[\\]\]+";
var word="(" + atom + "|(\"[^\"]*\"))";
var user_pattern = new RegExp("^" + word + "(\\." + word + ")*$");
var ip_pattern = /^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;
var domain_pattern = new RegExp("^" + atom + "(\\." + atom +")*$");

var arr = email.match(pattern);
if (!arr) return "Email address seems incorrect (check @ and .'s)";
if (!arr[1].match(user_pattern)) return "The username doesn't seem to be valid.";

var ip = arr[2].match(ip_pattern);
if (ip) {
for (var i=1; i<5; i++) if (ip[i] > 255) return "Destination IP address is invalid!";
}
else {
if (!arr[2].match(domain_pattern)) return "The domain name doesn't seem to be valid.";
var domain = arr[2].match(new RegExp(atom,"g"));
if (domain.length<2) return "This address is missing a hostname!";
if (domain[domain.length-1].length<2 || domain[domain.length-1].length>3)
return "The address must end in a three-letter domain, or two letter country.";
}
return false;
}<div class='small'>[이 게시물은 관리자님에 의해 2011-10-31 16:57:14 JavaScript에서 이동 됨]</div>