Through a practical combat, let's see how PWA is applied to Angular projects

This article will introduce you to Angular PWA Progressive Web Application, share a practical experience, and see how PWA is applied to Angular projects. I hope it will be helpful to everyone!

PWA has the following advantages:

• Availability in no-connection (offline) state
• Fast loading speed
• Screen shortcut

If circumstances permit, it is still recommended that you use it in projects to improve performance and user experience.

For more detailed instructions, please view MDN PWA. Talk is Cheap Next, let’s see the effect in practice. [Related tutorial recommendations: "angular tutorial"]

1 Preparation work

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

Modifypackage.json It is convenient for us to start the project

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

Create a new data.json file to simulate the data, just put it in the root directory

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

2 Write a small demo to simulate the future Get the data

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);
  }
}

Next we modify app.component.ts and app.component.html

// 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>

So far if the project is normal After starting up, you should see the following page

3 Disconnect from the Internet

After completing the preparations, let’s disconnect from the Internet and see what will happen. PressF12 Select NetWork and then select Offline.

After refreshing, you will find that our page can no longer load normally

4 PWA debut

Now it’s our turn for PWA.

First installpwa

ng add @angular/pwa

After the installation is complete, you will find that these files have changed

Here We mainly focus on the ngsw-config.json file. The changes in other files are easy to understand. Everyone will know at a glance

The files to be cached are defined in this file:

• favicon.ico
• index.html
• manifest.webmanifest
• JS and CSS bundles
• All files under assets

Next we configure the requested interface into ngsw-config.json, more For configuration, please refer to Angular Service Worker Configuration

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

Rebuild our project after the configuration is completednpm run build:pwa

After the build is completed, pass npm run start:pwa to start our project. After successful startup, open http://127.0.0.1:8001 and you should be able to see

We repeat the previous steps, disconnect the network and refresh again. You will find that the page can still be loaded normally.

Let’s test our cache again and follow the steps below to try it

1. Open an incognito browsing window first
2. npm run start:pwa starts, and opens the page
3. Close the tab (note that it is a tab, you cannot close the browser), turn off the http-server
4. to app.component. Make some changes to html
5. Rebuild and then start with http-server to open the page.

The result of the first startup

Change app.component.html Chinese text is Hello PWA Demo, run againnpm run build:pwa && npm run start:pwa and then openhttp://127.0.0.1:8001 and you will find that the result has not changed

At this time, if we refresh it again, we will find that the page has been refreshed to the one after our changes

5 Summary

For more related instructions, it is recommended that you refer to Angular official, and for related configurations, refer to Service Work Configuration. I hope this article can help everyone improve the performance and experience of front-end pages. Similarly, Angular also has a function App Shell, which is similar to the PWA we mentioned this time. Anyone who is interested can also check it out :).

DevUI: Experience makes the world a better place!

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