Angular - Trabalhando com criação dinâmica das configurações com base nas variáveis de ambiente

example_package.json

...
"scripts": {
    "ng": "ng",
    "config": "ts-node ./src/set-env.ts",
    "start": "npm run config -- --environment=dev && ng serve",
    "build": "npm run config && ng build --output-path=dist",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
...

set-env.ts

const fs = require('fs');
const yargs = require('yargs');

if(!yargs.argv.environment){
  const dotenv = require('dotenv');
  dotenv.config();
}

const targetPath = `./src/environments/environment.ts`;
const envConfigFile = `
export const environment = {
  production: true,
  url_api: "${process.env.URL_API}",
  token_name: "${process.env.TOKEN_NAME}",
};
`
fs.writeFile(targetPath, envConfigFile, function (err) {
  if (err) {
    console.log(err);
  }
  console.log(`Output generated at ${targetPath}`);
});