Question

I used preg_match for my server-side validation but I want to have a client side too.

For my PHP I allow those characters:

'/^[A-Za-z][a-zA-Z0-9 .:-,!?]+$/'

How would I make a white list of characters with match() in JavaScript?

EDIT:

I tried this but it didn’t work for some reason:

My debugger says, right before the if statement:

218SyntaxError: Invalid regular expression: range out of order in character class

$('#title').blur(function(){
      input = $('#title').val();
      var invalidChars = /^[^a-z][^a-z\d .:-,!?]+$/i;
    if (!invalidChars.test(input)){
         alert('true');     
         }
      else {
           alert('false');
           }
});

Answer 1

var validChars = /^[a-z][a-z\d .:\-,!?]+$/i;
if (validChars.test(myText)){ ... }

Using regex.test(str) is slightly more performant than str.match(regex) if all you want is to know if a match exists or not.

Alternatively, you can early out if you see any invalid character:

var invalidChars = /^[^a-z][^a-z\d .:\-,!?]+$/i;
if (!invalidChars.test(myStr)){
  // we passed
}

This allows the regex test to stop the moment it sees a disallowed character.