Get domain name for service in Angular2

You can use window, as others have stated, and to make it injectable, from ng6 and forward, you need an injection token.

Declare the token like this:

export const WINDOW = new InjectionToken('window',
    { providedIn: 'root', factory: () => window }
);

Then use it in the class constructor:

class Foo {
  constructor(@Inject(WINDOW) private window: Window) { }
}

As Window is an interface in TypeScript, if you don't do the injection like that, when you build the project for production you will get an error: Can't resolve all parameters for <ClassName>. And later another one: ERROR in : Error: Internal error: unknown identifier undefined.

To understand injection better, read the angular docs for DI: https://angular.io/guide/dependency-injection

I'm using plain javascript and URL native api for URL parsing:

declare var window: any; // Needed on Angular 8+
const parsedUrl = new URL(window.location.href);
const baseUrl = parsedUrl.origin;
console.log(baseUrl); // this will print http://example.com or http://localhost:4200

I test this on Angular 7 and it worked correctly

declare var window: any;

console.log (window.location.host); //result lrlucas.github.io > domain github pages

with window.location.host I get the full domain

Note: Declare the window variable before @Component

Just inject Document. Angular has a default implementation for Document. Document has a property called defaultView that has all the goodies like window.

import { DOCUMENT } from '@angular/common';
import { Inject, Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root'
})
export class HostnameService
{

  constructor(
    @Inject(DOCUMENT) private document: Document
  ) { }

  getHostname(): string
  {
    // Remember to use this.document as unscoped document also exists but is not mockable.
    return this.document.defaultView.window.location.hostname;

    // Or use the location on document.
    return this.document.location.hostname;

  }
}

There is no setup required elsewhere.