Validate regex of email

Question

I have a recipient textbox that allows to enter an email address and send to the person.As you know, there are regex to be considered when someone enters an email. For example, an email without @ is not an valid email.

So I wrote a function that checks the regex of an email like this:

//check email address
    function validateEmail(email) {
        var re = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
        return re.test(email);
    }

So if I write test@hotmail.com then this would be valid and test@@@hotmail.com would not be valid. Yes this works fine with no issue. However, in my textbox I am allowed to send to multiple recipients in this form:

test@hotmail.com,test123@hotmail.com,....

So if I enter the above,it will treat it as invalid but seeing that I am bad in regex expression, is there a way to allow this to go through?

Edit:

This is how my regular expression looks like:

var re = /(?:^|,)((([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))(?:$|(?=,)))/;

Possible duplicate of [How to validate an email address in JavaScript?](https://stackoverflow.com/questions/46155/how-to-validate-an-email-address-in-javascript) — Alexander Lallier, Apr 18 '19 at 12:17

CertainPerformance · Answer 1 · 2019-04-18T10:49:48.810

3

At the beginning of the pattern, add a non-capturing group for , or the beginning of the string:

(?:^|,)

And at the end of the pattern, add a non-capturing group for the end of the string, or lookahead for ,:

(?:$|(?=,))

This will allow multiple matches on a single line, if separated by commas.

(?:^|,)(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))(?:$|(?=,))
^^^^^^^                                                                                                                                                       ^^^^^^^^^^^

https://regex101.com/r/Dzyfqt/1

If you not only want to validate but extract the emails too, this will sometimes include a leading comma, which is probably undesirable - to fix that, enclose everything after the initial non-capturing group in another group:

(?:^|,)((([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))(?:$|(?=,)))

and the email address alone will be in the first captured group.

If you want to check to see if the string contains comma-separated email addresses, and nothing other than comma-separated email addresses, you can use the first pattern and replace every matching email with the empty string, and check to see if the final resulting string is empty:

function validateEmail(email) {
  var re = /(?:^|,)(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))(?:$|(?=,))/g;
  return email.replace(re, '') === '';
}
console.log(validateEmail('test@hotmail.com,test123@hotmail.com'));

edited Apr 18 '19 at 10:49

answered Apr 18 '19 at 10:26

CertainPerformance

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How does the entire thing look like? I am really bad at recognizing symbols – Daredevil Apr 18 '19 at 10:27
I see. So basically what it does, is it checks is there is a comma at the end of an `email`? – Daredevil Apr 18 '19 at 10:30
It will only validate an email if it starts (at the beginning of the string, or after a comma) and if it ends (at the end of the string, or right before another comma). – CertainPerformance Apr 18 '19 at 10:32
So it's will also check `,test@hotmail.com` as invalid right? What about `test@hotmail.com,`? – Daredevil Apr 18 '19 at 10:33
Tried your solution and key in `test@hotmail.com,test123@hotmail.com` but it still throws invalid. – Daredevil Apr 18 '19 at 10:35
Works just fine for me - check the regex101 link I posted in the answer https://regex101.com/r/Dzyfqt/1 – CertainPerformance Apr 18 '19 at 10:36
Checked my edited post. My syntax looks identical to yours solution – Daredevil Apr 18 '19 at 10:37
You mis-copied the pattern in the answer. You still have the start-of-string and end-of-string anchors *outside* the added capturing groups, so your current pattern will only match emails which start at the beginning of the string and end at the end of the string. – CertainPerformance Apr 18 '19 at 10:43
You're saying the second solution or the first solution you posted? – Daredevil Apr 18 '19 at 10:44
Either work - the pattern you're currently using isn't either of them. – CertainPerformance Apr 18 '19 at 10:45
What mistake did i make? I failed to see. Checked my edited – Daredevil Apr 18 '19 at 10:45
Look at my comment above: `You still have the start-of-string and end-of-string anchors *outside* the added capturing groups, so your current pattern will only match emails which start at the beginning of the string and end at the end of the string.` – CertainPerformance Apr 18 '19 at 10:46
Okay I get what you mean, can you double check if i'm correct? – Daredevil Apr 18 '19 at 10:48
Although there are some flaws that I tried though like `test@hotmail.com,test` will still go through – Daredevil Apr 18 '19 at 10:51
If you want to check that the whole string is composed of nothing more than comma-separated emails, you can't use `.test` (at least not with that pattern) - you can use `.replace` instead, see https://jsfiddle.net/nfp4mz7s/ – CertainPerformance Apr 18 '19 at 10:52
Good to know. It's true if it's `,test@hotmail.com` still goes through? – Daredevil Apr 18 '19 at 10:53
You can negative lookahead for `^` when you match `,` if you don't want that to be a match, I suppose – CertainPerformance Apr 18 '19 at 10:56
Using `.replace` will make this `test@hotmail.com,test212@hotmail.com` not go through – Daredevil Apr 18 '19 at 10:56
Oh wait, did you add a `g` at the end of the reg? I didn't notice you changed the reg, thought you only change the `.replace` – Daredevil Apr 18 '19 at 10:57
Ok tested your new solution it does work.Marked as accepted. Sorry i didn't mean to be a bother though. – Daredevil Apr 18 '19 at 11:00

score 0 · Accepted Answer · answered Apr 18 '19 at 10:51

Please Check with this Code :

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
 
</head>
  
<script>
 function sendmessage(){

        var recipient = document.getElementById("recipient").value; 
        var result=validateEmails(recipient);
        alert(result);
   
 }   
   function validateEmails(emailString) {
        var regex = /^([\w-\.]+@([\w-]+\.)+[\w-]{2,4})?$/;
        var result = emailString.replace(/\s/g, "").split(/,|;/);        
        for(var i = 0;i < result.length;i++) {
            if(!regex.test(result[i])) {
                return false;
            }
        }       
        return true;
    }
 
 
</script>  
  
<body>

&emsp;&emsp; To:<input type="email" style="font-size: 10pt;" size="70" id="recipient"><br><br>
  
  <div class="Send">
    <button type="button" style="font: 13px/1.231 Trebuchet MS;" onclick="sendmessage()"> Send </button>
</div>
  
</body>
</html>

Validate regex of email

2 Answers2