npm install mockjs --save-dev

import Mock from 'mockjs';
// GET請求
Mock.mock('/api/getData', 'get', () => {
  return Mock.mock({
    'data|10': [
      {
        'name': '@cname',
        'age|20-30': 1,
        'id|+1': 1
      }
    ]
  });
});
// POST請求
Mock.mock('/api/postData', 'post', (options) => {
  const { body } = options;
  return Mock.mock({
    'data': `hello, ${JSON.parse(body).name}!`
  });
});

import { Injectable } from '@angular/core';
import { HttpEvent, HttpHandler, HttpInterceptor, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs';
import { environment } from '../environments/environment';
import { MockService } from './mock.service';
@Injectable()
export class MockInterceptor implements HttpInterceptor {
  constructor(private mockService: MockService) {}
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    if (environment.useMock) { // 判斷是否開啟Mock.js
      const mockData = this.mockService.getMockData(req);
      if (mockData) {
        const response = new ResponseOptions({body: mockData});
        return Observable.of(new HttpResponse(response));
      }
    }
    return next.handle(req);
  }
}

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
import { AppComponent } from './app.component';
import { MockService } from './mock.service';
import { MockInterceptor } from './mock.interceptor';
@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    HttpClientModule
  ],
  providers: [
    MockService,
    {
      provide: HTTP_INTERCEPTORS,
      useClass: MockInterceptor,
      multi: true
    }
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

import { Component, OnInit } from '@angular/core';
import { HttpClient } from '@angular/common/http';
@Component({
  selector: "app-root",
  templateUrl: "./app.component.html",
  styleUrls: ["./app.component.css"],
})
export class AppComponent implements OnInit {
  title = "Mock.js Demo";
  data: any;
  name: string;
  constructor(private http: HttpClient) {}
  ngOnInit(): void {
    this.http.get("/api/getData").subscribe((res) => {
      this.data = res["data"];
    });
  }
  postData() {
    this.http.post("/api/postData", { name: this.name }).subscribe((res) => {
      alert(res["data"]);
    });
  }
}