JS Regex allowing incorrect characters

Question

I have a comments field for SEPA payments and such a field has the following restrictions when it comes to what a user can type:

a b c d e f g h i j k l m n o p          


        

Answer 1

The problem is due to the way you declared the regex via a RegExp constructor. The hyphen should be escaped twice to be treated as a literal hyphen there.

This is the range it allowed:

It is advised to use a literal notation when your regex is known from the start, and best practice is to use the hyphen at the end of the character class range in order to avoid escaping it.

To match 0 or more characters in your range, you need to use

var regex = /^[a-z0-9\/?:().,\'+\s-]*$/i;

See this demo fiddle

If you plan to match at least 1 (or more), keep your +? (or +, it will work the same way in your case) quantifier.

$('.no_special_chars').keypress(function (e) {   
  var regex = /^[a-z0-9\/?:().,\'+\s-]*$/i;
  console.log(String.fromCharCode(!e.charCode ? e.which : e.charCode));
  var str = String.fromCharCode(!e.charCode ? e.which : e.charCode);

  // Allow tab, left/right arrow, backspace and delete. Then proceed to validation
  if (e.keyCode == 9 || e.keyCode == 37 || e.keyCode == 39 || e.keyCode == 8 || e.keyCode == 46) {
     return true;
  }

  // Do not allow returns in the comment field
  if (e.keyCode == 13) {
     return false;
  }

  if (regex.test(str)) {
     return true;
  }

  return false;
});