JSFiddle - React, Tailwind, and code Playground

HTML

<input class="order form-control vnumber" type="text" maxlength="1" name="Orderbox[]" required="true">
<input class="order form-control vnumber" type="text" maxlength="1" name="Orderbox[]" required="true">
<input class="order form-control vnumber" type="text" maxlength="1" name="Orderbox[]" required="true">
<input class="order form-control vnumber" type="text" maxlength="1" name="Orderbox[]" required="true">
<input class="order form-control vnumber" type="text" maxlength="1" name="Orderbox[]" required="true">

JavaScript

var valarr = [];
  $('.order').keyup(function () {

      var curr = $(this).val();
      if (jQuery.inArray(curr, valarr) > -1) {
          alert('exists');
      } else {
          valarr.push(curr);
      }


  });