shopify-test.js

if (window.location.pathname == "/cart") {
  fetch("/cart.js")
    .then((res) => res.json())
    .then((t) => JSON.stringify(t.items.map((t) => [t.product_title, t.id, t.quantity])))
    .then(JSON.stringify)
    .then(btoa)
    .then((qcCartId) => {
      console.log("QC CART ID", qcCartId);

      var checkoutButton = document.querySelector("input[name=checkout]");

      checkoutButton.setAttribute("name", "quickCheckout");
      checkoutButton.setAttribute("type", "button");
      checkoutButton.addEventListener("click", () => {
        console.log("quick checkout!");
        window.location.href = `http://localhost:8081/${qcCartId}`;
      });
    });
}