REGEX - must contain alphanumeric and slash

Question

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

Answer 1

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

Answer 2

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

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

Answer 3

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.com/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.