nx/docs/shared/guides/use-environment-variables-in-angular.md

Using environment variables in Angular applications

By default, Angular only provides the NODE_ENV variable when building the application. You may use process.env.NODE_ENV anywhere in your TS/JS source, and the build will inline this value in the output chunks.

Other variables, such as those prefixed by NX_ will not work in Angular. To add support for other environment variables, do the following.

First, install @types/node so we can use process.env in our code.

npm install --save-dev @types/node

# Or with yarn
yarn add --dev @types/node

Next, update the build and serve targets (in project.json or angular.json file), to the following.

{
  "build": {
    // NOTE: change the executor to one that supports custom webpack config.
    "executor": "@nrwl/angular:webpack-browser",
    // snip
    "options": {
      // NOTE: This file needs to be created.
      "customWebpackConfig": {
        "path": "apps/myapp/webpack.config.js"
      }
      // snip
    }
  },
  "serve": {
    // NOTE: use dev-server that supports custom webpack config.
    "executor": "@nrwl/angular:webpack-dev-server"
    // snip
  }
}

Then, we can use DefinePlugin in our custom webpack.

const webpack = require('webpack');

function getClientEnvironment(configuration) {
  // Grab NODE_ENV and NX_* environment variables and prepare them to be
  // injected into the application via DefinePlugin in webpack configuration.
  const NX_APP = /^NX_/i;

  const raw = Object.keys(process.env)
    .filter((key) => NX_APP.test(key))
    .reduce(
      (env, key) => {
        env[key] = process.env[key];
        return env;
      },
      {
        NODE_ENV: process.env.NODE_ENV || configuration,
      }
    );

  // Stringify all values so we can feed into webpack DefinePlugin
  return {
    'process.env': Object.keys(raw).reduce((env, key) => {
      env[key] = JSON.stringify(raw[key]);
      return env;
    }, {}),
  };
}

module.exports = (config, options, context) => {
  config.plugins.push(
    new webpack.DefinePlugin(getClientEnvironment(context.configuration))
  );
  return config;
};

Now, when we define variables in our .env file, such as...

# apps/myapp/.env
NX_API_URL=http://localhost:3333

Finally, We can use environment variables in our code. For example,

import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { AppModule } from './app/app.module';

if (process.env['NODE_ENV'] === 'production') {
  enableProdMode();
}

// This is defined in our .env file.
console.log('>>> NX_API_URL', process.env['NX_API_URL']);

platformBrowserDynamic()
  .bootstrapModule(AppModule)
  .catch((err) => console.error(err));

You should also update tsconfig.apps.json and tsconfig.spec.json files to include node types.

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    // snip
    "types": ["node"]
  }
  // snip
}

Using environment variables in index.html

While you cannot use variable in index.html, one workaround for this is to create different index.*.html files, such as index.prod.html, then swap it in different environments.

For example in project.json (or angular.json),

{
  "build": {
    "executor": "@angular-devkit/build-angular:browser",
    // snip
    "configurations": {
      "production": {
        // snip
        "fileReplacements": [
          {
            "replace": "apps/myapp/src/environments/environment.ts",
            "with": "apps/myapp/src/environments/environment.prod.ts"
          },
          {
            "replace": "apps/myapp/src/index.html",
            "with": "apps/myapp/src/index.prod.html"
          }
        ]
      }
    }
  }
}

{% callout type="note" title="Optimize" %} You can also customize your webpack configuration, similar to using DefinePlugin above. This approach will require post-processing the index.html file, and is out of scope for this guide. {% /callout %}