javascript - REGEX - must contain alphanumeric and slash - Stack Overflow

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I am trying to do a validation that an input field must contain alpha numeric and slash as its value.

Eg: AA/AB/12314/2017/ASD

The above shown is the example of the value that should be the input field. I don't have any knowledge in writing the regular expressions. So please do help me.

Finally I came up with the below code:

var message = $('#message').val();

if (/^[a-zA-Z0-9-/]*$/.test($.trim(message)) == false)
{
    $('#message').focus();
    alert('invalid message');
}

I am trying to do a validation that an input field must contain alpha numeric and slash as its value.

Eg: AA/AB/12314/2017/ASD

The above shown is the example of the value that should be the input field. I don't have any knowledge in writing the regular expressions. So please do help me.

Finally I came up with the below code:

var message = $('#message').val();

if (/^[a-zA-Z0-9-/]*$/.test($.trim(message)) == false)
{
    $('#message').focus();
    alert('invalid message');
}

• javascript
• jquery
• regex

Share Improve this question Follow asked Mar 3, 2017 at 11:40 Ganesh RadhakrishnanGanesh Radhakrishnan 35011 gold badge55 silver badges1515 bronze badges 6

• 2 Even if some browsers allow using unescaped / inside the character class, it is still a good idea to escape it. What is the problem with your code? Note the - before / is treated as a literal -. – Wiktor Stribiżew Commented Mar 3, 2017 at 11:42
• is your string valid if it contains only alphanumeric characters? Or does it must contain both – Nino Commented Mar 3, 2017 at 11:46
• 1 @WiktorStribiżew A - is treated as a lteral - only if at the very beggining/end of a char class, am I wrong? Which isn't the case here. – sp00m Commented Mar 3, 2017 at 11:49
• 1 @sp00m most engines also treat it as literal if placed directly after a range, where it thus can't open a range. – Sebastian Proske Commented Mar 3, 2017 at 11:51
• @SebastianProske Just tried, you're right, thanks for the info! – sp00m Commented Mar 3, 2017 at 11:54

 |  Show 1 more ment

3 Answers 3

Sorted by: Reset to default 9

it must contain both alphanumeric and slash.

I understand that you may have 1+ alphanumeric symbols followed with at least 1 / followed with more alphanumeric symbols. You need to change the regex to /^[a-z\d]+(?:\/[a-z\d]+)+$/i:

var message = $('#message').val();
if (!/^[a-z\d]+(?:\/[a-z\d]+)+$/i.test($.trim(message)))
{
    $('#message').focus();
    alert('invalid message');
}

<script src="https://ajax.googleapis./ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input id="message" value="ASD/TD"/>

Details:

• ^ - start of string
• [a-z\d]+ - 1 or more letters or digits
• (?:\/[a-z\d]+)+ - 1 or more sequences of
  • \/ - slash
  • [a-z\d]+ - 1 or more letters or digits
• $ - end of string
• /i - a case insensitive modifier, so that [a-z] could also match uppercase ASCII letters.

If you mean there must be a / and alphanumeric anywhere inside the string, use lookaheads:

/^(?=[a-z\d]*\/)(?=\/*[a-z\d])[a-z\d\/]+$/i
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 

See the regex demo. Here, (?=[a-z\d]*\/) requires a / after 0+ alphanumerics, and (?=\/*[a-z\d]) requires an alphanumeric after 0+ slashes. [a-z\d\/]+ will match 1 or more alphanumeric or slashes.

escaping / like \/is a good practise but inside of char class, not necessary.
the * must be changed to +. because * will also match null.
also remove the - otherwise - will also be matched.

function validate(){
  var message = $('#message').val();

  if (/^[a-zA-Z0-9/]+$/.test($.trim(message)) == false){
      $('#message').focus();
     alert('invalid message');
  }
}

<script src="https://ajax.googleapis./ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<textarea id="message"></textarea><button onclick="validate();">Test</button>

function checkValidity(input){
	var onlyAlphaNum = /^[a-z0-9//]+$/
	return onlyAlphaNum.test(input);
}

var message = $('#message').val();
if(!checkValidity(message)){
	$('#message').focus();
    alert('invalid message');
}

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