Character whitelisting for input field

whitelist.js

(function($){
  // Bind to an input field. Provide chars, a string of characters.
  // Now only those characters can be typed in.
  $.fn.whitelist = function(chars){
    var $this = $(this), chars = chars.split(''); 
    $this.keypress(function(e){
      if (chars.indexOf(String.fromCharCode(e.which)) == -1){ return false; }});
    return $this;
  };
}(jQuery));