server.js

require("dotenv").config();
const express = require("express");
const app = express();
const { resolve } = require("path");
const stripe = require("stripe")(process.env.secret_key); // https://stripe.com/docs/keys#obtain-api-keys
app.use(express.static("."));
app.use(express.json());
// An endpoint for your checkout 
app.post("/checkout", async (req, res) => { 
  // Create or retrieve the Stripe Customer object associated with your user.
  let customer = await stripe.customers.create(); // This example just creates a new Customer every time

  // Create an ephemeral key for the Customer; this allows the app to display saved payment methods and save new ones
  const ephemeralKey = await stripe.ephemeralKeys.create(
    {customer: customer.id},
    {apiVersion: '2020-08-27'}
  );  

  // Create a PaymentIntent with the payment amount, currency, and customer
  const paymentIntent = await stripe.paymentIntents.create({
    amount: 123456,
    currency: "nzd",
    customer: customer.id
  });

  // Send the object keys to the client
  res.send({
    publishableKey: process.env.publishable_key, // https://stripe.com/docs/keys#obtain-api-keys
    paymentIntent: paymentIntent.client_secret,
    customer: customer.id,
    ephemeralKey: ephemeralKey.secret
  });
});

app.listen(process.env.PORT, () =>
  console.log(`Node server listening on port ${process.env.PORT}!`)
);