Create your own custom jQuery functions

custom-jquery-functions.html

<script>
  // Declaring a new jQuery function
  (function ($) {
    $.fn.newSuperCoolFunction = function () {
      return this.each(function (_, selector) {
        var elements = $(selector)

        elements.each(function (_, elementSelector) {
          var element = $(elementSelector);
          element.addClass('super-cool')
        });
      })
    }
  })(jQuery)

  // Call the new function
  $(document).ready(function() {
    $('button').newSuperCoolFunction();
  });

</script>

<button>
    Make me super cool
</button>

<button>
    Make me super cool
</button>