import { HttpClientModule } from '@angular/common/http';

@NgModule({
 imports: [
  BrowserModule,
  // import HttpClientModule after BrowserModule.
  HttpClientModule,
 ],
 declarations: [
  AppComponent,
 ],
 bootstrap: [ AppComponent ]
})

### base-interceptor.ts

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

/*設置請求的基地址，方便替換*/
const baseurl = 'http://localhost:8360';

@Injectable()
export class BaseInterceptor implements HttpInterceptor {

 constructor() {}

 intercept(req, next: HttpHandler) {

  let newReq = req.clone({
   url: req.hadBaseurl ? `${req.url}` : `${baseurl}${req.url}`,
  });
  /*此處設置額外的頭部，token常用于登陸令牌*/
  if(!req.cancelToken) {
  /*token數(shù)據(jù)來源自己設置，我常用localStorage存取相關數(shù)據(jù)*/
   newReq.headers =
   newReq.headers.set('token', 'my-new-auth-token')
  }

  // send cloned request with header to the next handler.
  return next.handle(newReq)
   .pipe(
    /*失敗時重試2次，可自由設置*/
    retry(2),
    /*捕獲響應錯誤，可根據(jù)需要自行改寫，我偷懶了，直接用的官方的*/
    catchError(this.handleError)
   )
 }
 
 private handleError(error: HttpErrorResponse) {
  if (error.error instanceof ErrorEvent) {
   // A client-side or network error occurred. Handle it accordingly.
   console.error('An error occurred:', error.error.message);
  } else {
   // The backend returned an unsuccessful response code.
   // The response body may contain clues as to what went wrong,
   console.error(
    `Backend returned code ${error.status}, ` +
    `body was: ${error.error}`);
  }
  // return an observable with a user-facing error message
  return throwError(
   'Something bad happened; please try again later.');
 };
}

### index.ts

import { HTTP_INTERCEPTORS } from '@angular/common/http';

import { BaseInterceptor } from './base-interceptor';

/** Http interceptor providers in outside-in order */
export const httpInterceptorProviders = [
 { provide: HTTP_INTERCEPTORS, useClass: BaseInterceptor, multi: true },

];

/*
Copyright 2017-2018 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

import { httpInterceptorProviders } from './http-interceptors/index'

@NgModule({
 declarations: [
  AppComponent
 ],
 imports: [
  BrowserModule,
  HttpClientModule
 ],
 providers: [
  httpInterceptorProviders
 ],
 bootstrap: [AppComponent]
})