How to validate multiple emails using Regex?

Question

After a quick research on the Stackoverflow, I wasn't able to find any solution for the multiple email validation using regex (split JS function is not applicable, but some reason back-end of the application waits for a string with emails separated by ;).

Here are the requirements:

Emails should be validated using the following rule: [A-Za-z0-9\._%-]+@[A-Za-z0-9\.-]+\.[A-Za-z]{2,4}
Regex should accept ; sign as a separator
Emails can be written on multiple lines, finishing with ;
Regex may accept the end of the line as ;

I come up with this solution:

^[A-Za-z0-9\._%-]+@[A-Za-z0-9\.-]+\.[A-Za-z]{2,4}(?:[;][A-Za-z0-9\._%-]+@[A-Za-z0-9\.-]+\.[A-Za-z]{2,4}?)*

but it doesn't work for point #3-4

So here are cases that are OK:

 1. [email protected];[email protected]
 2. [email protected];[email protected];
 3. [email protected];
    [email protected];
    [email protected];

Here are cases that are definetely NOT OK:

  1. [email protected] [email protected]
  2. [email protected],
  3. [email protected]
     [email protected]

All sort of help will be appreciated

Why is 3. not OK? According to rule 4, the regex may accept end of line as ; and the two emails are separated by an end of line? — mathematical.coffee
– mathematical.coffee, Commented Mar 20, 2012 at 3:27
(Also, could you split, validate, and then join back together to pass to the "back-end of the application"?) — mathematical.coffee
– mathematical.coffee, Commented Mar 20, 2012 at 3:46
So here is the short story: For a change on JavaScript code I have to write long reports that will take 3-4 days for approval, why did I change code that 'is no my scope' — John Smith
– John Smith, Commented Mar 20, 2012 at 4:02

Nicholas Carey · Accepted Answer · 2012-08-30 21:50:16Z

This is how I'm doing it (ASP.Net app, no jQuery). The list of email addresses is entered in a multi-line text box:

function ValidateRecipientEmailList(source, args)
{
  var rlTextBox     = $get('<%= RecipientList.ClientID %>');
  var recipientlist = rlTextBox.value;
  var valid         = 0;
  var invalid       = 0;

  // Break the recipient list up into lines. For consistency with CLR regular i/o, we'll accept any sequence of CR and LF characters as an end-of-line marker.
  // Then we iterate over the resulting array of lines
  var lines = recipientlist.split( /[\r\n]+/ ) ;
  for ( i = 0 ; i < lines.length ; ++i )
  {
    var line = lines[i] ; // pull the line from the array

    // Split each line on a sequence of 1 or more whitespace, colon, semicolon or comma characters.
    // Then, we iterate over the resulting array of email addresses
    var recipients = line.split( /[:,; \t\v\f\r\n]+/ ) ;
    for ( j = 0 ; j < recipients.length ; ++j )
    {
      var recipient = recipients[j] ;

      if ( recipient != "" )
      {
        if ( recipient.match( /^([A-Za-z0-9_-]+\.)*[A-Za-z0-9_-]+\@([A-Za-z0-9_-]+\.)+[A-Za-z]{2,4}$/ ) )
        {
          ++valid ;
        }
        else
        {
          ++invalid ;
        }
      }
    }

  }

  args.IsValid = ( valid > 0 && invalid == 0 ? true : false ) ;
  return ;
}

kirilloid · Accepted Answer · 2012-03-21 15:56:44Z

1

var email = "[A-Za-z0-9\._%-]+@[A-Za-z0-9\.-]+\.[A-Za-z]{2,4}";
var re = new RegExp('^'+email+'(;\\n*'+email+')*;?$');

[ "[email protected];[email protected]",
  "[email protected];[email protected];",
  "[email protected];\[email protected];\[email protected]",
  "[email protected] [email protected]",
  "[email protected],",
  "[email protected]\[email protected]" ].map(function(str){
    return re.test(str);
}); // [true, true, true, false, false, false]

answered Mar 21, 2012 at 15:56

kirilloid

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1 Comment

Vasanth Over a year ago

Not able to validate the following format. [email protected];dddd

Community · Accepted Answer · 2017-05-23 12:09:02Z

1

There is no reason not to use split - in the same way the backend will obviously do.

return str.split(/;\s*/).every(function(email) {
    return /.../.test(email);
}

For good or not-so-good email regular expressions have a look at Validate email address in JavaScript?.

edited May 23, 2017 at 12:09

CommunityBot

11 silver badge

answered Mar 21, 2012 at 16:28

Bergi

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