透過一個實戰，來看看PWA怎麼應用在Angular項目

npm i -g @angular/cli@latest
ng new pwa-demo
# npm i -g json-server
# npm i -g http-server

{
  ....,
  "scripts": {
    ...,
    "json": "json-server data.json -p 8000",
    "build:pwa": "ng build",
    "start:pwa": "http-server -p 8001 -c-1 dist/pwa-demo"
  }
}

{
  "posts": [{ "id": 1, "title": "json-server", "author": "typicode" }],
  "comments": [{ "id": 1, "body": "some comment", "postId": 1 }],
  "profile": { "name": "typicode" }
}

ng g s services/data

// data.service.ts
// 记得在 app.module.ts 中引入 HttpClientModule
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class DataService {
  dataUrl = 'http://localhost:8000/posts';

  constructor(private http: HttpClient) {}

  // 实际项目中最好别用 any，可以根据返回的数据类型定义对应的 interface
  public getPosts(): Observable<any> {
    return this.http.get(this.dataUrl);
  }
}

// app.component.ts
import { Component, OnInit } from '@angular/core';
import { DataService } from './services/data.service';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.scss']
})
export class AppComponent implements OnInit {
  title = 'pwa-demo';
  posts = [];

  constructor(private dataService: DataService) {}

  ngOnInit(): void {
    this.dataService.getPosts().subscribe((res) => {
      this.posts = res;
    });
  }
}

<div class="app">
  <h1>Hello PWA</h1>
  <br />
  {{ posts | json }}
</div>

ng add @angular/pwa

{
  ...,
  "dataGroups": [
    {
      "name": "api-posts",
      "urls": ["/posts"],
      "cacheConfig": {
        "maxSize": 100,
        "maxAge": "5d"
      }
    }
  ]
}