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;
    }
}