Using environment variables in Angular applications
Angular builders (e.g. @nx/angular:webpack-browser and @angular-devkit/build-angular:browser) don't have built-in support for using environment variables when building applications.
To add support for environment variables we need to use the webpack DefinePlugin in our own custom webpack configuration. We'll see how to do so in the following sections.
A note on NODE_ENV
The webpack-based Angular builders (e.g. @nx/angular:webpack-browser and @angular-devkit/build-angular:browser) set the webpack's mode configuration option based on the values for the following in the builder options:
optimizationoptimization.scriptsoptimization.stylesoptimization.styles.minify
If any of the above is set to true, webpack's mode is set to production. Otherwise, it's set to development.
By default, webpack automatically sets the NODE_ENV variable to the value of the mode configuration option. Therefore, Angular applications code have access to that environment variable at build time, but we can't change the NODE_ENV variable value directly as we would do with other environment variables because Angular always set the mode configuration option based on the above.
To change the NODE_ENV variable we can do one of the following:
- Turn on the builder optimizations to set it to
production - Turn off the builder optimizations to set it to
development - Use a custom webpack configuration to override the webpack
modeset by Angular builders
The first two options is a matter of changing your build target configuration or passing the specific flag in the command line. We'll see how to do the last in the following section.
Use a custom webpack configuration to support environment variables
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": "@nx/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": "@nx/angular:webpack-dev-server"
// snip
}
}
Then, we can use DefinePlugin in our custom webpack.
const webpack = require('webpack');
function getClientEnvironment() {
// Grab 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;
}, {});
// 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) => {
// Overwrite the mode set by Angular if the NODE_ENV is set
config.mode = process.env.NODE_ENV || config.mode;
config.plugins.push(new webpack.DefinePlugin(getClientEnvironment()));
return config;
};
Now, when we define variables in our .env file, such as...
# apps/myapp/.env
NX_API_URL=http://localhost:3333
Alternatively, you can set the variable when running a terminal command by using:
- MacOS & Linux:
NX_API_URL=http://localhost:9999 npm run build-prod - Windows:
set NX_API_URL=http://localhost:9999 & npm run build-prod
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"
}
]
}
}
}
}
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.