Progressive Web App

Arvin

What we will cover today

What is progressive web app (PWA) ?
What do you need to build a PWA ?
Demo
Some resources

What PWA want to do ?

Add to Home Screen
App-like
Offline support
Push notification
Splash Screen

Why we need PWA?

source: https://www.youtube.com/watch?v=MyQ8mtR9WxI

Provide user a better experience on the web.
More users will come.
It's a Win-win game.

PWA design principle

Progressive
Responsive
App-like
Fresh
Safe ( HTTPS )

Discoverable (manifest.json)
Re-engageable
Installable
Linkable

Supported by Service worker

Web Worker

Four kinds of worker :

Dedicated workers
Shared worker
Service worker
Audio worker

Web Workers provide a simple means for web content to run scripts in background threads.

Different scope with Window
Access global variable via Self

Can't manipulate DOM
Use postMessage() to communicate

http://mdn.github.io/simple-web-worker/

importScripts();

http://mdn.github.io/simple-shared-worker/

Service Worker

Javascript worker - can't manipulate DOM directly
Intercept network request
Promise
IndexDB may help

Register service-worker

(() => {
  if ('serviceWorker' in navigator) {
    navigator.serviceWorker.register('/sw.js').then(function(registration) {
      // Registration was successful
      console.log('ServiceWorker registration successful with scope: ',registration.scope);
    }).catch(function(err) {
      // registration failed :(
      console.log('ServiceWorker registration failed: ', err);
    });
  }  
})();

check your current service-worker: chrome://serviceworker-internals

service-worker lifecycle: Installing

const CACHE_NAME = 'my-site-cache-v1';
const urlsToCache = [
  '/',
  '/styles/main.css',
  '/script/main.js'
];

self.addEventListener('install', (event) => {
  // Perform install steps
  event.waitUntil(
    caches.open(CACHE_NAME)
      .then(function(cache) {
        console.log('Opened cache');
        return cache.addAll(urlsToCache);
      })
  );
});

mdn: cache api

App Shell

service-worker lifecycle: Fetch

self.addEventListener('fetch', (event) => {
  event.respondWith(
    caches.match(event.request)
      .then(function(response) {
        // Cache hit - return response
        if (response) {
          return response;
        }

        return fetch(event.request);
      }
    )
  );
});

mdn: fetch api

self.addEventListener('fetch', (event) => {
  event.respondWith(
    caches.match(event.request)
      .then(function(response) {
        // Cache hit - return response
        if (response) {
          return response;
        }

        // IMPORTANT: Clone the request. 
        let fetchRequest = event.request.clone();

        return fetch(fetchRequest).then(
            (response) => {
            // Check if we received a valid response
            if(!response || response.status !== 200 || response.type !== 'basic') {
              return response;
            }

            // IMPORTANT: Clone the response.
            let responseToCache = response.clone();

            caches.open(CACHE_NAME)
              .then((cache) => {
                cache.put(event.request, responseToCache);
              });

            return response;
          }
        );
      })
    );
});

Outside of service-worker lifecycle: Updating static cache

Updating

Update version of cache name in service-worker
We need to kill old cache

Outside of service-worker lifecycle: Updating static cache

self.addEventListener('activate', (e) => {  
  console.log('[ServiceWorker] Activate');  
  e.waitUntil(  
    caches.keys().then((keyList) => {  
      return Promise.all(keyList.map((key) => {  
        console.log('[ServiceWorker] Removing old cache', key);  
        if (key !== cacheName) {  
          return caches.delete(key);  
        }  
      }));  
    })  
  );  
});

PWA design principle

Progressive
Responsive
App-like
Fresh
Safe ( HTTPS )

Discoverable (manifest.json)
Re-engageable
Installable
Linkable

Manifest.json

Web App Manifest

Have a nice Icon on homescreen
Full screen mode, no more url bar!
Control screen orientation。
Splash screen setting
Tracking your app open from app or url

{
  "name": "REACT PWA",
  "short_name": "REACT PWA",
  "icons": [{
    "src": "images/icons/icon-128x128.png",
      "sizes": "128x128",
      "type": "image/png"
    }, {
      "src": "images/icons/icon-144x144.png",
      "sizes": "144x144",
      "type": "image/png"
    }, {
      "src": "images/icons/icon-152x152.png",
      "sizes": "152x152",
      "type": "image/png"
    }, {
      "src": "images/touch/icon-192x192.png",
      "sizes": "192x192",
      "type": "image/png"
    }, {
      "src": "images/touch/icon-256x256.png",
      "sizes": "256x256",
      "type": "image/png"
    }],
  "start_url": "/",
  "display": "standalone",
  "background_color": "#3E4EB8",
  "theme_color": "#2F3BA2"
}

One more thing...

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>React PWA</title>
  <link rel="manifest" href="/manifest.json">

  <meta name="apple-mobile-web-app-capable" content="yes">
  <meta name="apple-mobile-web-app-status-bar-style" content="black">
  <meta name="apple-mobile-web-app-title" content="PWA">
</head>
<body>
  <div id='app'>
  </div>
<script type="text/javascript" src="bundle.510aef2ba974480fc6df.js"></script></body>
</html>