Using Environment Variables in Angular Applications

For Angular applications using ESBuild

Setting the `define` option of the `application` executor

In Angular applications using the @nx/angular:application or @angular-devkit/build-angular:application executors, you can set the define option in the build target to define variables that will be available in your application code at build time:

{
  ...
  "targets": {
    "build": {
      "executor": "@nx/angular:application",
      "options": {
        ...
        "define": {
          "MY_API_URL": "http://localhost:3333"
        }
      }
    },
    ...
  }
}

Next, make sure to inform TypeScript of the defined variables to prevent type-checking errors during the build. We can achieve this in a number of ways. For example you could create or update a type definition file included in the TypeScript build process (e.g. src/types.d.ts) with declare statements for the defined variables:

declare const MY_API_URL: string;

The above would allow you to use the MY_API_URL variable in your application code as in the following example:

import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class ApiHttpClient {
  constructor() {
    console.log('API URL:', MY_API_URL);
  }
}

You can also define the variables in a way that allows you to consume them as you would do in Node.js applications:

{
  ...
  "targets": {
    "build": {
      "executor": "@nx/angular:application",
      "options": {
        ...
        "define": {
          "process.env.MY_API_URL": "http://localhost:3333"
        }
      }
    },
    ...
  }
}

Like the previous example, you must configure TypeScript to recognize the process.env object. You can do this by defining the process.env object in a type definition file:

declare const process: {
  env: {
    API_URL: string;
  };
};

And then use the variable in your application code:

import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class ApiHttpClient {
  constructor() {
    console.log('API URL:', process.env.MY_API_URL);
  }
}

Using a custom ESBuild plugin

The previous method is useful to statically define variables in the project configuration that will be available at build time. However, if you need to dynamically collect and define the environment variables available at build time, you can create a custom ESBuild plugin.

You can provide a custom ESBuild plugin to the @nx/angular:application or @nx/angular:browser-esbuild executors:

{
  ...
  "targets": {
    "build": {
      "executor": "@nx/angular:application",
      "options": {
        ...
        "plugins": ["apps/my-app/plugins/env-var-plugin.js"]
      }
    },
    ...
  }
}

Next, create the custom ESBuild plugin:

const myOrgEnvRegex = /^MY_ORG_/i;

const envVarPlugin = {
  name: 'env-var-plugin',
  setup(build) {
    const options = build.initialOptions;

    const envVars = {};
    for (const key in process.env) {
      if (myOrgEnvRegex.test(key)) {
        envVars[key] = process.env[key];
      }
    }

    options.define['process.env'] = JSON.stringify(envVars);
  },
};

module.exports = envVarPlugin;

The plugin collects all environment variables that start with MY_ORG_ and defines them in the process.env object. You can adjust the plugin to your needs (e.g., use a different regular expression, use a whitelist, add all environment variables, etc.).

As shown in the previous section, add the defined variables to a type definition file to ensure TypeScript recognizes them.

Now, you can define variables in an .env file, such as:

MY_ORG_API_URL=http://localhost:3333

Finally, you can use the environment variables in your application code:

import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class ApiHttpClient {
  constructor() {
    console.log('API URL:', process.env.MY_ORG_API_URL);
  }
}

For Angular applications using Webpack

Angular executors for Webpack (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 executors (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:

optimization
optimization.scripts
optimization.styles
optimization.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 mode set by Angular executors

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

Update the build and serve targets to use the @nx/angular relevant executors and provide a custom Webpack configuration:

{
  ...
  "targets": {
    "build": {
      "executor": "@nx/angular:webpack-browser",
      "options": {
        ...
        "customWebpackConfig": {
          "path": "apps/my-app/webpack.config.js"
        }
      }
    },
    "serve": {
      "executor": "@nx/angular:dev-server"
      ...
    },
    ...
  }
}

Then, we can use DefinePlugin in our custom Webpack configuration:

const webpack = require('webpack');

const myOrgEnvRegex = /^MY_ORG_/i;

function getClientEnvironment() {
  const envVars = {};
  for (const key in process.env) {
    if (myOrgEnvRegex.test(key)) {
      envVars[key] = process.env[key];
    }
  }

  return {
    'process.env': JSON.stringify(envVars),
  };
}

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;
};

In our custom Webpack configuration we collect all environment variables that start with MY_ORG_, define the process.env object with them, and provide it to the DefinePlugin. You can adjust the configuration to your needs (e.g., use a different regular expression, use a whitelist, add all environment variables, etc.).

declare const process: {
  env: {
    MY_ORG_API_URL: string;
  };
};

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

MY_ORG_API_URL=http://localhost:3333

Finally, we can use environment variables in our code:

import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class ApiHttpClient {
  constructor() {
    console.log('API URL:', process.env.MY_ORG_API_URL);
  }
}

Using environment variables in `index.html`

While you cannot use environment variables in index.html, one workaround is to create different index.*.html files, such as index.prod.html, then swap them in different environments.

For example, you can configure your build target in project.json as follows:

{
  ...
  "targets": {
    "build": {
      "executor": "@angular-devkit/build-angular:browser",
      ...
      "configurations": {
        "production": {
          ...
          "fileReplacements": [
            {
              "replace": "apps/my-app/src/index.html",
              "with": "apps/my-app/src/index.prod.html"
            }
          ]
        }
      }
    }
  }
}