Check out example codes for "firebase not found in envirorment.ts file angular". It will help you in understanding the concepts better.

Code Example 1

// When you run ng build --prod angular-cli will use the environment.prod.ts file
// and your environment.prod.ts files environment variable doesn't have the firebase
// field hence you are getting the exception.

export const environment = {
  production: true,
  firebase: {
    apiKey: "...",
    authDomain: "project.firebaseapp.com",
    databaseURL: "https://project.firebaseio.com",
    projectId: "project",
    storageBucket: "project.appspot.com",
    messagingSenderId: "..."
  }
};

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