Cloudflare Workers

Cloudflare Workers is a JavaScript edge runtime on Cloudflare CDN.

You can develop the application locally and publish it with a few commands using Wrangler. Wrangler includes trans compiler, so we can write the code with TypeScript.

Let’s make your first application for Cloudflare Workers with Hono.

1. Setup

A starter for Cloudflare Workers is available. Start your project with "create-hono" command. Select cloudflare-workers template for this example.

npm

npm create hono@latest my-app

yarn

yarn create hono my-app

pnpm

pnpm create hono my-app

bun

bun create hono@latest my-app

deno

deno init --npm hono my-app

Move to my-app and install the dependencies.

npm

cd my-app
npm i

yarn

cd my-app
yarn

pnpm

cd my-app
pnpm i

bun

cd my-app
bun i

2. Hello World

Edit src/index.ts like below.

import { Hono } from 'hono'
const app = new Hono()

app.get('/', (c) => c.text('Hello Cloudflare Workers!'))

export default app

3. Run

Run the development server locally. Then, access http://localhost:8787 in your web browser.

npm

npm run dev

yarn

yarn dev

pnpm

pnpm dev

bun

bun run dev

Change port number

If you need to change the port number you can follow the instructions here to update wrangler.toml / wrangler.json / wrangler.jsonc files: Wrangler Configuration

Or, you can follow the instructions here to set CLI options: Wrangler CLI

4. Deploy

If you have a Cloudflare account, you can deploy to Cloudflare. In package.json, $npm_execpath needs to be changed to your package manager of choice.

npm

npm run deploy

yarn

yarn deploy

pnpm

pnpm run deploy

bun

bun run deploy

That's all!

Using Hono with other event handlers

You can integrate Hono with other event handlers (such as scheduled) in Module Worker mode.

To do this, export app.fetch as the module's fetch handler, and then implement other handlers as needed:

const app = new Hono()

export default {
  fetch: app.fetch,
  scheduled: async (batch, env) => {},
}

Serve static files

If you want to serve static files, you can use the Static Assets feature of Cloudflare Workers. Specify the directory for the files in wrangler.toml:

assets = { directory = "public" }

Then create the public directory and place the files there. For instance, ./public/static/hello.txt will be served as /static/hello.txt.

.
├── package.json
├── public
│   ├── favicon.ico
│   └── static
│       └── hello.txt
├── src
│   └── index.ts
└── wrangler.toml

Types

You have to install @cloudflare/workers-types if you want to have workers types.

npm

npm i --save-dev @cloudflare/workers-types

yarn

yarn add -D @cloudflare/workers-types

pnpm

pnpm add -D @cloudflare/workers-types

bun

bun add --dev @cloudflare/workers-types

Testing

For testing, we recommend using @cloudflare/vitest-pool-workers. Refer to examples for setting it up.

If there is the application below.

import { Hono } from 'hono'

const app = new Hono()
app.get('/', (c) => c.text('Please test me!'))

We can test if it returns "200 OK" Response with this code.

describe('Test the application', () => {
  it('Should return 200 response', async () => {
    const res = await app.request('http://localhost/')
    expect(res.status).toBe(200)
  })
})

Bindings

In the Cloudflare Workers, we can bind the environment values, KV namespace, R2 bucket, or Durable Object. You can access them in c.env. It will have the types if you pass the "type struct" for the bindings to the Hono as generics.

type Bindings = {
  MY_BUCKET: R2Bucket
  USERNAME: string
  PASSWORD: string
}

const app = new Hono<{ Bindings: Bindings }>()

// Access to environment values
app.put('/upload/:key', async (c, next) => {
  const key = c.req.param('key')
  await c.env.MY_BUCKET.put(key, c.req.body)
  return c.text(`Put ${key} successfully!`)
})

Using Variables in Middleware

This is the only case for Module Worker mode. If you want to use Variables or Secret Variables in Middleware, for example, "username" or "password" in Basic Authentication Middleware, you need to write like the following.

import { basicAuth } from 'hono/basic-auth'

type Bindings = {
  USERNAME: string
  PASSWORD: string
}

const app = new Hono<{ Bindings: Bindings }>()

//...

app.use('/auth/*', async (c, next) => {
  const auth = basicAuth({
    username: c.env.USERNAME,
    password: c.env.PASSWORD,
  })
  return auth(c, next)
})

The same is applied to Bearer Authentication Middleware, JWT Authentication, or others.

Deploy from GitHub Actions

Before deploying code to Cloudflare via CI, you need a Cloudflare token. You can manage it from User API Tokens.

If it's a newly created token, select the Edit Cloudflare Workers template, if you already have another token, make sure the token has the corresponding permissions(No, token permissions are not shared between Cloudflare Pages and Cloudflare Workers).

then go to your GitHub repository settings dashboard: Settings->Secrets and variables->Actions->Repository secrets, and add a new secret with the name CLOUDFLARE_API_TOKEN.

then create .github/workflows/deploy.yml in your Hono project root folder, paste the following code:

name: Deploy

on:
  push:
    branches:
      - main

jobs:
  deploy:
    runs-on: ubuntu-latest
    name: Deploy
    steps:
      - uses: actions/checkout@v4
      - name: Deploy
        uses: cloudflare/wrangler-action@v3
        with:
          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}

then edit wrangler.toml, and add this code after compatibility_date line.

main = "src/index.ts"
minify = true

Everything is ready! Now push the code and enjoy it.

Load env when local development

To configure the environment variables for local development, create a .dev.vars file or a .env file in the root directory of the project. These files should be formatted using the dotenv syntax. For example:

SECRET_KEY=value
API_TOKEN=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9

For more about this section you can find in the Cloudflare documentation: https://developers.cloudflare.com/workers/wrangler/configuration/#secrets

Then we use the c.env.* to get the environment variables in our code.

INFO

By default, process.env is not available in Cloudflare Workers, so it is recommended to get environment variables from c.env. If you want to use it, you need to enable nodejs_compat_populate_process_env flag. You can also import env from cloudflare:workers. For details, please see How to access env on Cloudflare docs

type Bindings = {
  SECRET_KEY: string
}

const app = new Hono<{ Bindings: Bindings }>()

app.get('/env', (c) => {
  const SECRET_KEY = c.env.SECRET_KEY
  return c.text(SECRET_KEY)
})

Before you deploy your project to Cloudflare, remember to set the environment variable/secrets in the Cloudflare Workers project's configuration.

For more about this section you can find in the Cloudflare documentation: https://developers.cloudflare.com/workers/configuration/environment-variables/#add-environment-variables-via-the-dashboard