Async JavaScript - Creating promises and handling promise chains.

index.js

/**
 * @author doodercodes
 * @description Async JavaScript - Creating promises and handling promise chains.
 * @description JAVASCRIPT WAITS FOR NOTHING!
 * @date 08/03/2023
 **/

const cart = randCart();

createOrder(cart)
  .then((orderID) => orderID)
  // .catch((err) => console.error(`\r\nERROR: ${err.message}`))
  .then((orderID) => proceedToPayment(orderID))
  .catch((err) => console.error(`\r\nERROR: ${err.message}`))
  .then((paymentInfo) => {
    if (!paymentInfo) return;
    console.log(paymentInfo);
  });

function createOrder(cart) {
  return new Promise((resolve, reject) => {
    if (!validateCart(cart)) {
      const error = new Error("Cart is not valid");
      reject(error);
      return null;
    }

    let orderID = id();
    console.log("Creating order...");
    console.info(cart);
    console.info(orderID);

    function id() {
      let orderID = null;
      function randID() {
        for (let i = 0; i <= Math.floor(Math.random() * 4); i++) {
          switch (i) {
            case 0:
              orderID = "";
            case 1:
              orderID = 1;
              break;
            case 2:
              orderID = "19982002-MS";
              break;
            case 3:
              orderID = "57548345-HF";
              break;
          }
        }

        if (orderID === "") return null;
        return orderID;
      }
      return randID();
    }

    setTimeout(() => {
      if (!orderID) orderID = null;
      resolve(orderID);
    }, 2000);
  });
}

function proceedToPayment(orderID) {
  return new Promise((resolve, reject) => {
    if (!orderID || typeof orderID !== "string" || orderID === "") {
      const error = new Error(
        `orderID is null or contains the wrong datatype\r\norderID: ${orderID}`
      );
      reject(error);
      return;
    }

    console.log(`OrderID Created: ${orderID}`);
    resolve("Payment successful");
  });
}

function randCart() {
  let cart = null;
  for (let i = 0; i <= Math.floor(Math.random() * 3); i++) {
    switch (i) {
      case 0:
        cart = ["shoes", "pants", "kurta"];
        break;
      case 1:
        cart = [];
        break;
      case 2:
        cart = 0;
        break;
    }
  }
  return cart;
}

function validateCart(cart) {
  return cart.length == 0 || !Array.isArray(cart) ? false : true;
}