关于Angular2请求拦截器

import { Injectable } from '@angular/core';
import { Observable } from 'rxjs';
import { MessagesService } from 'app/shared/service';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpHeaders, HttpEvent, HttpErrorResponse, HttpResponse } from '@angular/common/http';
import { catchError, map } from 'rxjs/operators';
import { LoginService } from 'app/auth/login.service';

@Injectable()
export class RequestInterceptor implements HttpInterceptor {
    constructor(private msg: MessagesService, private ls: LoginService) {}

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any> | any> {
        let _headers = new HttpHeaders()
            .set('Authorization', this.ls.getAccessToken() + '')
            // .set('X-Requested-With', 'XMLHttpRequest')
            // .set('Content-Type', 'application/json')
            .set('Accept', '*/*')
            .set('token', `${localStorage.getItem('token')}`)
            .set('roleId', `${localStorage.getItem('role_id')}`)
            .set('userId', `${localStorage.getItem('user_id')}`)
            .set('tenantId', `${localStorage.getItem('tenant_id')}`);
            // .set('userName', localStorage.getItem('user_name') || '');

        const body = req.body;
        const isFormData = body instanceof FormData;

        req.headers.keys().forEach(item => {
            _headers = _headers.set(item, req.headers.get(item));
        });

        const authReq = req.clone({
            headers: _headers
        });
        // 针对导入文件为post请求body参数为FormData类型的接口
        const importreq = req.clone({
            headers: _headers
        });
        console.log(authReq);
        // console.log(importreq);

        return next.handle(isFormData ? importreq : authReq).pipe(
             // 对所有接口进行登陆超时拦截，跳转登陆页面
            // map((event: any) => {
            //     if (event instanceof HttpResponse) {
            //       if (event.body && event.body.code === 300) {
            //         this.ls.logIn();
            //       } else {
            //           return event;
            //       }
            //     }
            // }),
            catchError((err: HttpErrorResponse) => {
                this.handleError(err.status);
                throw err;
            })
        );
    }

    // 报错信息
    handleError(status) {
        if (status === 0) {
            this.msg.error(`${status} please checkout the network`);
        } else if (status === 401) {
            // this.msg.error(`user token out of date`);
            // this.ls.logOut();
        } else if (status === 404) {
            this.msg.error('The requested resource does not exist');
        } else if (status === 500) {
            this.msg.error('server error, please try again later');
        } else {
            // this.msg.error('未知错误，请检查网络');
            console.error('an unknown error');
        }
    }
}