API Routes in Angular 18 Server Side Rendering

In this guide, I will walk you through setting up API routes in a server-side rendered Angular 18 application, leveraging Express to create RESTful endpoints.

Prerequisites

You’ll need the following:

Node.js 18 or later

Create a new Angular Application
Adding an API Route in server.ts
Configuring app.config.ts for HttpClient
Fetching Data in app.component.ts
Running the Server in SSR Mode

Create a new Angular Application

Let’s get started by creating a new Angular project. Execute the following commands:

npm install -g @angular/cli@latest
ng new angular-ssr-api-routes

ng new is the recommended way to scaffold an Angular project quickly.

When prompted, choose:

CSS for the stylesheet format
y for enabling Server-Side Rendering (SSR) and Static Site Generation (SSR/Prerendering)

Once that is done, move into the project directory and start the app in development mode by executing the following command:

cd angular-ssr-api-routes
npm run start

The app should be running on localhost:4200.

In angular.json, set "prerender": false to ensure the application only uses server-side rendering without prerendering.

Adding an API Route in server.ts

Next, define an API route in server.ts to serve data for your SSR application. Open server.ts and add the following code:

// File: server.ts // [!code focus]

// ...

// Example Express Rest API endpoints
// server.get('/api/**', (req, res) => { });
// Serve static files from /browser
server.get('**', express.static(browserDistFolder, {
    maxAge: '1y',
    index: 'index.html',
}));

server.get('/api/data', (req, res) => { // [!code ++] // [!code focus]
    res.json({ code: 1 }); // [!code ++] // [!code focus]
}) // [!code ++] // [!code focus]

// ...

This route (/api/data) will return a JSON response { code: 1 }, which can be fetched by the Angular application.

Configuring app.config.ts for HttpClient

In order to fetch data from our new API endpoint, make sure HttpClient is set up using fetch. Open app.config.ts and add provideHttpClient:

// File: app.config.ts // [!code focus]

import { ApplicationConfig, provideZoneChangeDetection } from '@angular/core';
import { provideRouter } from '@angular/router';

import { routes } from './app.routes';
import { provideClientHydration } from '@angular/platform-browser';
import { provideHttpClient, withFetch } from '@angular/common/http'; // [!code ++] // [!code focus]

export const appConfig: ApplicationConfig = {
  providers: [
    provideZoneChangeDetection({ eventCoalescing: true }),
    provideRouter(routes),
    provideClientHydration(),
    provideHttpClient(withFetch()), // [!code ++] // [!code focus]
  ],
};

Fetching Data in app.component.ts

To retrieve data from the API route on the client side, open app.component.ts and set up a simple data-fetching function that runs on component initialization:

// File: app.component.ts  // [!code focus]

import { isPlatformBrowser } from '@angular/common'; // [!code ++] // [!code focus]
import { Component, Inject, OnInit, PLATFORM_ID } from '@angular/core'; // [!code ++] // [!code focus]
import { RouterOutlet } from '@angular/router';

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [RouterOutlet],
  templateUrl: './app.component.html',
  styleUrl: './app.component.css',
})
export class AppComponent implements OnInit {
  isBrowser: boolean; // [!code ++] // [!code focus]
  title = 'with-angular';
  constructor(@Inject(PLATFORM_ID) platformId: Object) { // [!code ++] // [!code focus]
    this.isBrowser = isPlatformBrowser(platformId); // [!code ++] // [!code focus]
  } // [!code ++] // [!code focus]
  async ngOnInit() { // [!code ++] // [!code focus]
    if (this.isBrowser) { // [!code ++] // [!code focus]
      const fetchCall = await fetch('/api/data'); // [!code ++] // [!code focus]
      const fetchResp = await fetchCall.json(); // [!code ++] // [!code focus]
      // Do something // [!code ++] // [!code focus]
    } // [!code ++] // [!code focus]
  } // [!code ++] // [!code focus]
}

In this setup:

isPlatformBrowser is used to ensure the API call only happens on the client side, not on the server side.
The component fetches data from the /api/data endpoint upon initialization and logs it to the console.

Running the Server in SSR Mode

To test your API routes in server-side rendering mode, you need to build and serve the Angular application:

In one terminal:

npm run watch

In a separate terminal, run:

npm run serve:ssr:angular-ssr-api-routes

Your application, now with server-side rendering and API routing, should be accessible at localhost:4200.

Conclusion

In this guide, we covered how to set up API routes for server-side rendering in an Angular 18 application. Using this approach, you can serve data dynamically from the server and enhance your application’s performance with server-rendered content.

If you have any questions or comments, feel free to reach out to me on Twitter.