Web Workers,
Service Workers,
and PWA's

Thank you!

Who is Michael Cole?

michael@powma.com

Full-stack. JavaScript. DevOps.

Freelancer.  Technologist.

Web Workers,
Service Workers,
and PWA's

Thank you!

Reglar Web Pages

Reglar Web Pages

  • Reglar HTML/CSS/JS
     

  • Shift-Esc in Chrome​ to see processes
     

  • Limited access to CPU/Memory/Disk​​

    • One process per tab/plugin/extension

    • Can't access memory of other tabs

    • LocalStorage/Cookies/Etc.

Reglar Web Pages


 


 

  • One process per tab/plugin/extension

  • Can't access memory of other tab

Web Workers

  • Create multiple processes

  • Pass messages between them

Web Workers

// index.html - regular web page <script>

// Create worker, using code from your site
w = new Worker('worker.js');

// Listen for results.
w.addEventListener('message', function(event) {
  var el = document.getElementById('result');
  el.innerHTML += event.data + '\n';
});

// Send data to worker
setTimeout(function() {
  console.log('page sends message ...');
  w.postMessage('Hello from Page!'); 
}, 2000);

Web Workers

  • Multiple processes

  • Communicate between them

// worker.js

// Listen for messages from main page w/ string for outgoing messages.
var task = 'Hello from Worker!';

var r = self.addEventListener('message', function(e) {
  console.log('... worker got message ' + e.data);
  task = e.data;
}, false);

// Fibonacci numbers generator.  
// F(0) = 0, F(1) = 1, F(x) = (F(x-2) + F(x-1).
function F(x) { 
  if (x<2) return x;  return F(x-1) + F(x-2); 
}

// Send messages with Fibonacci numbers and task string
var i = 0;
setInterval(function() {
  self.postMessage(F(i++) + ' ' + task);
}, 200);

// Don't use while(true) {}, or message events won't be processed

  • Multiple processes

  • Messages between (not shared memory)

  • caniuse.com: 96.8%

  • No DOM access (no jQuery, etc)

    • ​importScripts(url, url)

    • Network via new XMLHttpRequest() or Fetch()

  • Practical applications: 

    • Browser Cryptominer Malware

    • PDF.js

Web Workers

Ctrl-shift-i

Web Workers

 

Questions?

Service Workers

Service Workers

  • caniuse.com => 91.54%

  • Next Version: Edge, Safari, iOS Safari

Service Workers

Code:   https://github.com/MichaelJCole/talk_webworkers

  • All that

  • A JavaScript proxy, to edit responses
    of your page's network requests

  • Installation life-cycle

  • Push Notifications, etc.

What is a Proxy?

"A Proxy is an intermediary
for requests from clients seeking resources
from other servers."

What is a Proxy?

"A Proxy is an intermediary
for requests from clients seeking resources
from other servers."

HEAD

What is a Proxy?

"A Proxy is an intermediary
for requests from clients seeking resources
from other servers."

Browser

Service Worker

"A JavaScript proxy, to edit responses
of your page's network requests

Service Workers

  • Web Worker

  • A JavaScript proxy, to edit responses
    of your page's network requests

  • Installation Life-cycle

  • Push Notifications

Service Workers

Installation Life-Cycle

  • Register (from index.html)
    ServiceWorkerContainer.register(scriptURL, options).then(...)
     
  • Browser Downloads (redownloads ~every 24 hrs)
    Updated ServiceWorker scripts wait until "activated"
     
  • Installs, then Activates
    Service Worker listens for events
     
  • Proxy requests with "FetchEvent" FetchEvent.respondWith(stuff)

Service Workers

Register?  Install?  Notifications?

 

This sounds like a Native App.

 

Example? 

 

https://googlechrome.github.io/samples/service-worker/basic/

 

See also: https://serviceworke.rs/

Service Workers

Register?  Install?  Notifications?

 

This sounds like a Native App.

 

Example?  Vue.js PWA starter template.

$ npm install -g vue-cli
$ vue init pwa my-project
$ cd my-project
$ npm install
$ npm run dev
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