Angular HttpInterceptor 不更改 header

Question

我编写了一个 Angular (4.3.6) HttpInterceptor 来添加一些 header 字段，但如果我在调试器中检查它们，则 header 不会更新。有什么想法吗？

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

@Injectable()
export class AuthInterceptor implements HttpInterceptor {


    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

        console.log('AuthInterceptor at work');

        const contentTypeReq = req.clone({
            headers: req.headers.set('Content-Type', 'application/json')
        });

        const token  = localStorage.getItem('token');
        if (token) {
            const authReq = contentTypeReq.clone({
                headers: req.headers.set('Authorization', 'Bearer ' + token)
            });
            return next.handle(authReq);
        }

        // Pass on the cloned request instead of the original request.
        return next.handle(contentTypeReq);
    }
}

Answer 1

他们很懒惰。例如keys method看起来像:

keys(): string[] {
    this.init(); <== initialize

    return Array.from(this.normalizedNames.values());
}

如果你想检查它们，只需调用:

req.headers.keys()

如果你想检查值，你可以使用 get 或 getAll 方法:

req.headers.getAll('Content-Type')

或者您可以从控制台调用init 方法，然后您将能够在headers Map 中看到标题

而且当angular adds headers to request它使用 forEach也调用 init 方法的方法。