从 .env 设置 Angular 6 环境变量

Question

There's an angular 6 project using environment variables from ./project/src/environments/environment.prod.ts

export const environment = {
  production: true,
  testVar: 'gg',
};

The backend for this project also has env variables in a .env file, so a lot of variable duplicate angular env variables. It would be nice to have something like

export const environment = {
  production: true,
  testVar: process.env.TEST_VAR
};

, so I didn't have to duplicate variables.

ie

I'd like to parse variables from a .env file and assign their values to angular env variables during typescript compilation on the server.

How can this be done? Maybe with webpack?

UPDATE

Some clarification. My .env file contains no json. It looks like this:

TEST_VAR=1

UPDATE

Since ng eject is not available for Angular 6 , I don't seem to be able to hack into webpack config. Looks like deadend here.

ng eject

Overview

Temporarily disabled.

Ejects your app and output the proper webpack configuration and scripts.

Answer 1

You can create a config file and populate in Run-time.

1) create a File(app-config.json) in assets folder with your variables

{ "servicesUrl": "https://localhost:8080/api"}

2) create a service (AppConfigService ) to read the file.

@Injectable()
    export class AppConfigService {
        private appConfig;

        constructor (private injector: Injector) { }

        loadAppConfig() {
            let http = this.injector.get(HttpClient);

            return http.get('/assets/app-config.json')
            .toPromise()
            .then(data => {
                this.appConfig = data;
            })
        }

        get config() {
            return this.appConfig;
        }

3) Next we need to tell our application to execute the loadAppConfig() method of our service.

import { NgModule, APP_INITIALIZER } from '@angular/core';
import { AppConfigService } from './services/app-config.service';

@NgModule({
   ...,
    providers: [
        AppConfigService,
        {
            provide: APP_INITIALIZER,
            useFactory: appInitializerFn,
            multi: true,
            deps: [AppConfigService]
        }
    ],
    ...
})
export class AppModule { } 

4) create a function called "appInitializerFn" to call our service in AppModule (app.module.ts)

const appInitializerFn = (appConfig: AppConfigService) => {
    return () => {
        return appConfig.loadAppConfig();
    }
};

...

@NgModule({
    ...
})
export class AppModule {}

5) import environment and use it :example

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { AppConfigService } from './services/app-config.service';

@Injectable()
export class DataContextService {
    basePath: string;

    constructor (private environment: AppConfigService, private http: HttpClient) {
        this.basePath = environment.config.servicesBasePath;
    }

    getNames() {
        return this.http.get(this.basePath + '/names/');
    }
}

for more information please see: link

Answer 2

This question becomes also more and more important, when we want to containerize angular applications.

My research lead me to an idea, where I have to write a little node.js or typescript program, using dotenv for reading .env file and create the environment.ts file at buildtime, before starting ng serve. You can create entries in the package.json like this:

...
"config": "ts-node set-env.ts",
"server": "npm run config && ng serve"
...

and run it with

npm run server

Here is a good explanation with an example typescript file: https://medium.com/@ferie/how-to-pass-environment-variables-at-building-time-in-an-angular-application-using-env-files-4ae1a80383c

Answer 3

If you want to use variables in build time you could use dotenv

As early as possible in your application, require and configure dotenv.

require('dotenv').config()

Create a .env file in the root directory of your project. Add environment-specific variables on new lines in the form of NAME=VALUE. For example:

DB_HOST=localhost
DB_USER=root
DB_PASS=s1mpl3