Angular · Theory
An interceptor sits on every HTTP call. Add an Authorization header. Log errors. Retry once. Provide it with withInterceptors or HTTP_INTERCEPTORS.
Board: clone the request, set Bearer token from auth, pass to next. If 401, navigate to login. Trap: intercepting and forgetting to call next.handle — the request never leaves.
Add token + 401 → login. Must call next.
import { Component } from "@angular/core";
@Component({
selector: "app-root",
template: `
<h1>{{ title }}</h1>
<button (click)="toggle()">Toggle</button>
<p *ngIf="open">Panel open</p>
`,
})
export class AppComponent {
title = "Angular practice";
open = true;
toggle() {
this.open = !this.open;
}
}HTTP Interceptors: toggle open. Say whether the panel is on screen after one click.