Shopify Ajax API - Add Item to cart

product.liquid

<script>
var items = ['id': VARIANT_ID,'quantity': 1];

function addToCart(items){

  let formData = {
    'items': items
  };

  fetch(window.Shopify.routes.root + 'cart/add.js', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(formData)
  })

  .then(response => {
    alert('Added Product To Cart');
    return response.json();
  })

  .catch((error) => {
      console.error('Error:', error);
  });

}
</script>

<button onclick="addToCart(items)">Add to Cart</button>