Sign in
Skip to solution
hardFrontend

What is an InjectionToken?

874 views
01

Understand the problem

Explain InjectionToken.

diinjection-token
02

Attempt it yourself

Sketch your approach before reading the solution — that's what interviews test.

Nudge consolestandby

Stuck? Beam a request up — the console returns a conceptual nudge that guides your logic without spoiling the implementation.

03

Study the solution

An InjectionToken is a unique key for injecting values that aren't classes — config objects, primitives, or interfaces (which don't exist at runtime). You provide it with { provide: TOKEN, useValue: ... } and inject it via @Inject(TOKEN) or inject(TOKEN).

Solution ready — 2 min read

Classified // press E to declassify

04

Read the code

Define, provide, and inject a token
import { InjectionToken, inject, Component } from '@angular/core';

export interface AppConfig { apiUrl: string; retries: number; }
export const APP_CONFIG = new InjectionToken<AppConfig>('app.config');

@Component({
  selector: 'app-root',
  standalone: true,
  providers: [
    { provide: APP_CONFIG, useValue: { apiUrl: '/api', retries: 3 } },
  ],
  template: '<p>{{ cfg.apiUrl }} (retries: {{ cfg.retries }})</p>',
})
export class AppComponent {
  cfg = inject(APP_CONFIG);   // typed as AppConfig
}
05

Join the discussion

Discussion (0)

Sign in to join the discussion.

No responses yet. Be the first to share what you think.

Transmission complete // awaiting log

KEEP THE
STREAK ALIVE.

Dossier 91 of 121 decoded in the Angular track. One more won't hurt.

Back to track