Shopify - Apply Discount / Coupon / Promo Code on cart page

cartDiscount.liquid

<div class="cart-promo">
  <h2>ENTER A PROMO CODE</h2>
  <input type="text" id="devPromo">
  <a href="/checkout?discount=none" id="redemDevPromo">Apply Coupon</a>
</div>
<script>
  $(document).ready(function(){
    //listen to the promo button click
    $('#redemDevPromo').on('click', function(event){
      //disable the button event
      event.preventDefault();
      //write the url format
      var theUrl = '/checkout?discount=';
      //grab the discount code from the input
      var theDiscount = $('#devPromo').val();
      //full url to redirect to checkout with promo code
      var toRedirect = theUrl+theDiscount;
      console.log(toRedirect);
      //redirect
      window.location.href = toRedirect;
    });
  });
</script>

Hi! This code is amazing. I do have a request if you are still there? Is it possible the discount can be updated on the same page instead of redirecting to the checkout page? This way my customers can just choose paypal? Thank you!

Hii, The discount code is not applied to the checkout, plus it is also showing the error in the checkout page. Could you please suggest me something to correct this.