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 [email protected] 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:

[email protected],[email protected],....

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? — Alexander Lallier
– Alexander Lallier, Commented Apr 18, 2019 at 12:17

CertainPerformance · Accepted Answer · 2019-04-18 10:49:48Z

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('[email protected],[email protected]'));

edited Apr 18, 2019 at 10:49

answered Apr 18, 2019 at 10:26

CertainPerformance

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20 Comments

Daredevil Over a year ago

How does the entire thing look like? I am really bad at recognizing symbols

Daredevil Over a year ago

I see. So basically what it does, is it checks is there is a comma at the end of an email?

CertainPerformance Over a year ago

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).

Daredevil Over a year ago

So it's will also check ,[email protected] as invalid right? What about [email protected],?

Daredevil Over a year ago

Tried your solution and key in [email protected],[email protected] but it still throws invalid.

|

Ajinkya · Accepted Answer · 2019-04-18 10:51:23Z

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>

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