Add Stripe TypeScript Example

examples/with-stripe-typescript/.env.example

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+# Stripe keys
+STRIPE_PUBLISHABLE_KEY=pk_12345
+STRIPE_SECRET_KEY=sk_12345
+STRIPE_WEBHOOK_SECRET=whsec_1234

examples/with-stripe-typescript/.gitignore

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+.env
+.DS_Store
+.vscode
+
+# Node files
+node_modules/
+
+# Typescript
+dist
+
+# Next.js
+.next
+.now

examples/with-stripe-typescript/README.md

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+# Example using Stripe with TypeScript and react-stripe-js 🔒💸
+
+- Demo: https://nextjs-typescript-react-stripe-js.now.sh/
+- CodeSandbox: https://codesandbox.io/s/nextjs-typescript-react-stripe-js-rqrss
+- Tutorial: https://dev.to/thorwebdev/type-safe-payments-with-next-js-typescript-and-stripe-2a1o
+
+This is a full-stack TypeScript example using:
+
+- Frontend:
+  - Next.js and [SWR](https://github.com/zeit/swr)
+  - [react-stripe-js](https://github.com/stripe/react-stripe-js) for [Checkout](https://stripe.com/checkout) and [Elements](https://stripe.com/elements)
+- Backend
+  - Next.js [API routes](https://nextjs.org/docs/api-routes/introduction)
+  - [stripe-node with TypeScript](https://github.com/stripe/stripe-node#usage-with-typescript)
+
+### Included functionality
+
+- Making `.env` variables available to next: [next.config.js](next.config.js)
+  - **_NOTE_**: when deploying with Now you need to [add your secrets](https://zeit.co/docs/v2/serverless-functions/env-and-secrets) and specify a [now.json](/now.json) file.
+- Implementation of a Layout component that loads and sets up Stripe.js and Elements for usage with SSR via `loadStripe` helper: [components/Layout.tsx](components/Layout.tsx).
+- Stripe Checkout
+  - Custom Amount Donation with redirect to Stripe Checkout:
+    - Frontend: [pages/donate-with-checkout.tsx](pages/donate-with-checkout.tsx)
+    - Backend: [pages/api/checkout_sessions/](pages/api/checkout_sessions/)
+    - Checkout payment result page that uses [SWR](https://github.com/zeit/swr) hooks to fetch the CheckoutSession status from the API route: [pages/result.tsx](pages/result.tsx).
+- Stripe Elements
+  - Custom Amount Donation with Stripe Elements & PaymentIntents (no redirect):
+    - Frontend: [pages/donate-with-elements.tsx](pages/donate-with-checkout.tsx)
+    - Backend: [pages/api/payment_intents/](pages/api/payment_intents/)
+- Webhook handling for [post-payment events](https://stripe.com/docs/payments/accept-a-payment#web-fulfillment)
+  - By default Next.js API routes are same-origin only. To allow Stripe webhook event requests to reach our API route, we need to add `micro-cors` and [verify the webhook signature](https://stripe.com/docs/webhooks/signatures) of the event. All of this happens in [pages/api/webhooks/index.ts](pages/api/webhooks/index.ts).
+- Helpers
+  - [utils/api-helpers.ts](utils/api-helpers.ts)
+    - helpers for GET and POST requests.
+  - [utils/stripe-helpers.ts](utils/stripe-helpers.ts)
+    - Format amount strings properly using `Intl.NumberFormat`.
+    - Format amount for usage with Stripe, including zero decimal currency detection.
+
+## How to use
+
+### Using `create-next-app`
+
+Execute [`create-next-app`](https://github.com/zeit/next.js/tree/canary/packages/create-next-app) with [npm](https://docs.npmjs.com/cli/init) or [Yarn](https://yarnpkg.com/lang/en/docs/cli/create/) to bootstrap the example:
+
+```bash
+npm init next-app --example with-stripe-typescript with-stripe-typescript-app
+# or
+yarn create next-app --example with-stripe-typescript with-stripe-typescript-app
+```
+
+### Download manually
+
+Download the example:
+
+```bash
+curl https://codeload.github.com/zeit/next.js/tar.gz/canary | tar -xz --strip=2 next.js-canary/examples/with-stripe-typescript
+cd with-stripe-typescript
+```
+
+### Required configuration
+
+Copy the `.env.example` file into a file named `.env` in the root directory of this project:
+
+```bash
+cp .env.example .env
+```
+
+You will need a Stripe account ([register](https://dashboard.stripe.com/register)) to run this sample. Go to the Stripe [developer dashboard](https://stripe.com/docs/development#api-keys) to find your API keys and replace them in the `.env` file.
+
+```bash
+STRIPE_PUBLISHABLE_KEY=<replace-with-your-publishable-key>
+STRIPE_SECRET_KEY=<replace-with-your-secret-key>
+```
+
+Now install the dependencies and start the development server.
+
+```bash
+npm install
+npm run dev
+# or
+yarn
+yarn dev
+```
+
+### Forward webhooks to your local dev server
+
+First [install the CLI](https://stripe.com/docs/stripe-cli) and [link your Stripe account](https://stripe.com/docs/stripe-cli#link-account).
+
+Next, start the webhook forwarding:
+
+```bash
+stripe listen --forward-to localhost:3000/api/webhooks
+```
+
+The CLI will print a webhook secret key to the console. Set `STRIPE_WEBHOOK_SECRET` to this value in your `.env` file.
+
+### Deploy it to the cloud with ZEIT Now
+
+Install [Now](https://zeit.co/now) ([download](https://zeit.co/download))
+
+Add your Stripe [secrets to Now](https://zeit.co/docs/v2/serverless-functions/env-and-secrets):
+
+```bash
+now secrets add stripe_publishable_key pk_***
+now secrets add stripe_secret_key sk_***
+now secrets add stripe_webhook_secret whsec_***
+```
+
+To start the deploy, run:
+
+```bash
+now
+```
+
+After the successful deploy, Now will show you the URL for your site. Copy that URL (`https://your-url.now.sh/api/webhooks`) and create a live webhook endpoint [in your Stripe dashboard](https://stripe.com/docs/webhooks/setup#configure-webhook-settings).
+
+**_Note_** that your live webhook will have a different secret. To update it in your deployed application you will need to first remove the existing secret and then add the new secret:
+
+```bash
+now secrets rm stripe_webhook_secret
+now secrets add stripe_webhook_secret whsec_***
+```
+
+As the secrets are set as env vars in the project at deploy time, we will need to redeploy our app after we made changes to the secrets. Run `now` again to redeploy with the new secret value.

examples/with-stripe-typescript/components/CheckoutForm.tsx

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+import React, { useState } from 'react'
+
+import CustomDonationInput from '../components/CustomDonationInput'
+
+import { fetchPostJSON } from '../utils/api-helpers'
+import { formatAmountForDisplay } from '../utils/stripe-helpers'
+import * as config from '../config'
+
+import { useStripe } from '@stripe/react-stripe-js'
+
+const CheckoutForm: React.FunctionComponent = () => {
+  const [input, setInput] = useState({ customDonation: config.MIN_AMOUNT })
+  const stripe = useStripe()
+
+  const handleInputChange: React.ChangeEventHandler<HTMLInputElement> = e =>
+    setInput({
+      ...input,
+      [e.currentTarget.name]: e.currentTarget.value,
+    })
+
+  const handleSubmit: React.FormEventHandler<HTMLFormElement> = async e => {
+    e.preventDefault()
+    // Create a Checkout Session.
+    const response = await fetchPostJSON('/api/checkout_sessions', {
+      amount: input.customDonation,
+    })
+
+    if (response.statusCode === 500) {
+      console.error(response.message)
+      return
+    }
+
+    // Redirect to Checkout.
+    const { error } = await stripe!.redirectToCheckout({
+      // Make the id field from the Checkout Session creation API response
+      // available to this file, so you can provide it as parameter here
+      // instead of the {{CHECKOUT_SESSION_ID}} placeholder.
+      sessionId: response.id,
+    })
+    // If `redirectToCheckout` fails due to a browser or network
+    // error, display the localized error message to your customer
+    // using `error.message`.
+    console.warn(error.message)
+  }
+
+  return (
+    <form onSubmit={handleSubmit}>
+      <CustomDonationInput
+        name={'customDonation'}
+        value={input.customDonation}
+        min={config.MIN_AMOUNT}
+        max={config.MAX_AMOUNT}
+        step={config.AMOUNT_STEP}
+        currency={config.CURRENCY}
+        onChange={handleInputChange}
+      />
+      <button type="submit" disabled={!stripe}>
+        Donate {formatAmountForDisplay(input.customDonation, config.CURRENCY)}
+      </button>
+    </form>
+  )
+}
+
+export default CheckoutForm

examples/with-stripe-typescript/components/CustomDonationInput.tsx

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+import React from 'react'
+import { formatAmountForDisplay } from '../utils/stripe-helpers'
+
+type Props = {
+  name: string
+  value: number
+  min: number
+  max: number
+  currency: string
+  step: number
+  onChange: (e: React.ChangeEvent<HTMLInputElement>) => void
+}
+
+const CustomDonationInput: React.FunctionComponent<Props> = ({
+  name,
+  value,
+  min,
+  max,
+  currency,
+  step,
+  onChange,
+}) => (
+  <label>
+    Custom donation amount ({formatAmountForDisplay(min, currency)}-
+    {formatAmountForDisplay(max, currency)}):
+    <input
+      type="number"
+      name={name}
+      value={value}
+      min={min}
+      max={max}
+      step={step}
+      onChange={onChange}
+    ></input>
+  </label>
+)
+
+export default CustomDonationInput

examples/with-stripe-typescript/components/ElementsForm.tsx

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+import React, { useState } from 'react'
+
+import CustomDonationInput from '../components/CustomDonationInput'
+import PrintObject from '../components/PrintObject'
+
+import { fetchPostJSON } from '../utils/api-helpers'
+import { formatAmountForDisplay } from '../utils/stripe-helpers'
+import * as config from '../config'
+
+import { CardElement, useStripe, useElements } from '@stripe/react-stripe-js'
+
+const ElementsForm: React.FunctionComponent = () => {
+  const [input, setInput] = useState({
+    customDonation: config.MIN_AMOUNT,
+    cardholderName: '',
+  })
+  const [payment, setPayment] = useState({ status: 'initial' })
+  const [errorMessage, setErrorMessage] = useState('')
+  const stripe = useStripe()
+  const elements = useElements()
+
+  const PaymentStatus = ({ status }: { status: string }) => {
+    switch (status) {
+      case 'processing':
+      case 'requires_payment_method':
+      case 'requires_confirmation':
+        return <h2>Processing...</h2>
+
+      case 'requires_action':
+        return <h2>Authenticating...</h2>
+
+      case 'succeeded':
+        return <h2>Payment Succeeded 🥳</h2>
+
+      case 'error':
+        return (
+          <>
+            <h2>Error 😭</h2>
+            <p>{errorMessage}</p>
+          </>
+        )
+
+      default:
+        return null
+    }
+  }
+
+  const handleInputChange: React.ChangeEventHandler<HTMLInputElement> = e =>
+    setInput({
+      ...input,
+      [e.currentTarget.name]: e.currentTarget.value,
+    })
+
+  const handleSubmit: React.FormEventHandler<HTMLFormElement> = async e => {
+    e.preventDefault()
+    setPayment({ status: 'processing' })
+
+    // Create a PaymentIntent with the specified amount.
+    const response = await fetchPostJSON('/api/payment_intents', {
+      amount: input.customDonation,
+    })
+    setPayment(response)
+
+    if (response.statusCode === 500) {
+      setPayment({ status: 'error' })
+      setErrorMessage(response.message)
+      return
+    }
+
+    // Get a reference to a mounted CardElement. Elements knows how
+    // to find your CardElement because there can only ever be one of
+    // each type of element.
+    const cardElement = elements!.getElement(CardElement)
+
+    // Use your card Element with other Stripe.js APIs
+    const { error, paymentIntent } = await stripe!.confirmCardPayment(
+      response.client_secret,
+      {
+        payment_method: {
+          card: cardElement!,
+          billing_details: { name: input.cardholderName },
+        },
+      }
+    )
+
+    if (error) {
+      setPayment({ status: 'error' })
+      setErrorMessage(error.message ?? 'An unknown error occured')
+    } else if (paymentIntent) {
+      setPayment(paymentIntent)
+    }
+  }
+
+  return (
+    <>
+      <form onSubmit={handleSubmit}>
+        <CustomDonationInput
+          name="customDonation"
+          value={input.customDonation}
+          min={config.MIN_AMOUNT}
+          max={config.MAX_AMOUNT}
+          step={config.AMOUNT_STEP}
+          currency={config.CURRENCY}
+          onChange={handleInputChange}
+        />
+        <fieldset>
+          <legend>Your payment details:</legend>
+          <label>
+            Cardholder name:
+            <input
+              type="Text"
+              name="cardholderName"
+              onChange={handleInputChange}
+              required={true}
+            />
+          </label>
+          <CardElement
+            options={{
+              style: {
+                base: {
+                  fontSize: '16px',
+                  color: '#424770',
+                  '::placeholder': {
+                    color: '#aab7c4',
+                  },
+                },
+                invalid: {
+                  color: '#9e2146',
+                },
+              },
+            }}
+          />
+        </fieldset>
+        <button
+          type="submit"
+          disabled={
+            !['initial', 'succeeded', 'error'].includes(payment.status) ||
+            !stripe
+          }
+        >
+          Donate {formatAmountForDisplay(input.customDonation, config.CURRENCY)}
+        </button>
+      </form>
+      <PaymentStatus status={payment.status} />
+      <PrintObject content={payment} />
+    </>
+  )
+}
+
+export default ElementsForm