What are some use cases for Angular interceptors?

What are some common use cases for Angular interceptors?

Angular interceptors are used for various purposes, such as adding authentication tokens, logging requests, handling errors, and modifying request/response data.

Can you give me an example of how to use an interceptor for authentication?

Sure! You can create an interceptor that adds an authorization header to every outgoing request. Here's a simple example:

import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const cloned = req.clone({
      headers: req.headers.set('Authorization', 'Bearer YOUR_TOKEN_HERE')
    });
    return next.handle(cloned);
  }
}

What about error handling? How can interceptors help with that?

Interceptors can catch HTTP errors globally. You can create an interceptor that checks for error responses and handles them accordingly, like showing a notification or redirecting the user. Here's a basic example:

import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest, HttpErrorResponse } from '@angular/common/http';
import { Observable, throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';

@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(req).pipe(
      catchError((error: HttpErrorResponse) => {
        // Handle the error here
        console.error('Error occurred:', error);
        return throwError(error);
      })
    );
  }
}