How to easily add environment variables to an Angular application

This guide assumes that you already have an angular application set up by ng create and are using Angular CLI for compilation.

Other guides that I've read rely upon re-writing your environments/environment.ts|environment.prod.ts files with each compilation. I find this to be completely unnecessary when angular's internal use of webpack can just be extended to include environment variables.

1. Add @angular-builders/custom-webpack to your dev-dependencies

$ npm i -D @angular-builders/custom-webpack

1.a. Add dotenv to your dev-dependencies

I use dotenv to load .env file variables on my development machine. It is not required to install, but is useful while developing locally.

$ npm i -D dotenv

2. Create a custom webpack configuration

For example, create a file custom-webpack.config.js in the root of your project.

After creating the custom webpack file, add the following contents (or more) to the file.

const { EnvironmentPlugin } = require('webpack');
// Add additional requirements here

// If you're using dotenv
require('dotenv').config()

// Export a configuration object
// See [Wepack's documentation](https://webpack.js.org/configuration/) for additional ideas of how to 
// customize your build beyond what Angular provides.
module.exports = {
  plugins: [
    new EnvironmentPlugin([
      // Insert the keys to your environment variables here.
      // Eg: APP_API_ENDPOINT="http://localhost:3000/api/v1"
      APP_API_ENDPOINT
    ])
}

3. Add @angluar-builder/custom-webpack to your build scheme

In the fileangular.json, find the key projects.${YOUR PROJECT NAME}.architect.build and change it to:

...
"architect": {
  ...
  "build": {
    "builder: "@angular-builders/custom-webpack:browser",
    "options: {
      "path": "./custom-webpack.config.js",
      "replaceDuplicatePlugins": true
    }
    ...
  }
  ...
}
...

3.a Add @angular-builders/custom-webpack's development server

If you're using ng serve in developemnt, you may wish to also install the custom development server.

$ npm i -D @angular-builders/dev-server

And in your angular.json file, replace the dev server invocation to:

...
"architect": {
  ...
  "serve": {
    "builder": "@angular-builders/dev-server:dev-server",
    ...
  }
  ...
}
...

4. Use process.env to input your environment variables at compilation.

Perform the same steps as you'd use normally for the webpack EnvironmentPlugin.

Eg:

@Injectable()
export class ApiService {
  private readonly api = process.env.APP_API_ENDPOINT;
  
  constructor(private http: HttpClient) {  }
  
  public get(loc: string): Observable<any> {
    return this.http.get(api + loc);
  }
}