js 正则验证url

var reg = '[a-zA-z]+://[^\s]*';//正则
var url = $('#add [name=notice_url]').val();
if(url.length >0){
var reg_test = new RegExp(reg);
var result = reg_test.test(url);
if(result != 1){
PopAlert('地址填写错误');
return;
}
}