Integrate other frameworks with Express.js

With some additional configuration, you can build on the basic framework-aware CLI functionality to extend integration support to frameworks other than Angular and Next.js.

Before you begin

Before you get started deploying your app to Firebase, review the following requirements and options:

• Firebase CLI version 12.1.0 or later. Make sure to install the CLI using your preferred method.
• Optional: Billing enabled on your Firebase project (required if you plan to use SSR)

Initialize Firebase

To get started, initialize Firebase for your framework project. Use the Firebase CLI for a new project, or modify firebase.json for an existing project.

Initialize a new project

1. In the Firebase CLI, enable the web frameworks preview:

   firebase experiments:enable webframeworks

2. Run the initialization command from the CLI and then follow the prompts:

   firebase init hosting

3. Answer yes to "Do you want to use a web framework? (experimental)"

4. Choose your hosting source directory; this could be an existing web app.

5. If prompted, choose Express.js / custom

Initialize an existing project

Change your hosting config in firebase.json to have a source option, rather than a public option. For example:

{
  "hosting": {
    "source": "./path-to-your-express-directory"
  }
}

Serve static content

Before deploying static content, you'll need to configure your application.

Configure

In order to know how to deploy your application, the Firebase CLI needs to be able to both build your app and know where your tooling places the assets destined for Hosting. This is accomplished with the npm build script and CJS directories directive in package.json.

Given the following package.json:

{
    "name": "express-app",
    "version": "0.0.0",
    "scripts": {
        "build": "spack",
        "static": "cp static/* dist",
        "prerender": "ts-node prerender.ts"
    },
    …
}

The Firebase CLI only calls your build script, so you’ll need to ensure that your build script is exhaustive.

{
    "name": "express-app",
    "version": "0.0.0",
    "scripts": {
        "build": "spack && npm run static && npm run prerender",
        "static": "cp static/* dist",
        "prerender": "ts-node prerender.ts"
    },
    …
}

If your framework doesn’t support pre-rendering out of the box, consider using a tool like Rendertron. Rendertron will allow you to make headless Chrome requests against a local instance of your app, so you can save the resulting HTML to be served on Hosting.

Finally, different frameworks and build tools store their artifacts in different places. Use directories.serve to tell the CLI where your build script is outputting the resulting artifacts:

{
    "name": "express-app",
    "version": "0.0.0",
    "scripts": {
        "build": "spack && npm run static && npm run prerender",
        "static": "cp static/* dist",
        "prerender": "ts-node prerender.ts"
    },
    "directories": {
        "serve": "dist"
    },
    …
}

Deploy

After configuring your app, you can serve static content with the standard deployment command:

firebase deploy

Serve Dynamic Content

To serve your Express app on Cloud Functions for Firebase, ensure that your Express app (or express-style URL handler) is exported in such a way that Firebase can find it after your library has been npm packed.

To accomplish this, ensure that your files directive includes everything needed for the server, and that your main entry point is set up correctly in package.json:

{
    "name": "express-app",
    "version": "0.0.0",
    "scripts": {
        "build": "spack && npm run static && npm run prerender",
        "static": "cp static/* dist",
        "prerender": "ts-node tools/prerender.ts"
    },
    "directories": {
        "serve": "dist"
    },
    "files": ["dist", "server.js"],
    "main": "server.js",
    ...
}

Export your express app from a function named app:

// server.js
export function app() {
  const server = express();
   …
   return server;
}

Or if you’d rather export an express-style URL handler, name it handle:

export function handle(req, res) {
   res.send(‘hello world’);
}

Deploy

firebase deploy

This deploys your static content to Firebase Hosting and allows Firebase to fall back to your Express app hosted on Cloud Functions for Firebase.

Optional: integrate with Firebase Authentication

The web framework-aware Firebase deploy tooling will automatically keep client and server state in sync using cookies. To access the authentication context, the Express res.locals object optionally contains an authenticated Firebase App instance (firebaseApp) and the currently signed in User (currentUser).