The Web

beyond websites

István Szmozsánszky "Flaki"

@slsoftworks

JavaScript Developer

Mozilla Contributor
&
Community TechSpeaker

Tessel Project
Team Member

Frontend Trainer at
DPC Consulting

New standardized browser APIs

Offline: Cache API, indexedDB

Sensors: Geolocation, Battery, Accelerometer

Hardware: Web Bluetooth, Web NFC

Authentication: Credentials API

What are service workers?

    A kind of clientside server, scriptable proxy —    worker script tied to the origin, rather the page.

Promises (ES 2015) & Fetch API (DOM)

Easier handling of async network requests - and async callbacks in general.

Arrow functions (ES 2015)

fetch("data.json").then(function(p) {
  return p.json();
} ).then( function(c) {
  console.log(c);
});

fetch("data.json")
  .then( p => p.json() )
  .then( c => console.log(c) );
a => x

(a, b) => { return x; });

(function(a, b) { return x; }).bind(this);

The service worker life cycle

bitsofco.de/the-service-worker-lifecycle

// Note: ONLY HTTPS!
navigator.serviceWorker.register('/serviceworker.js', {

  // Service Worker events are scoped
  // to this subfolder only
  scope: '/trained-to-thrill/'

}).then(function(reg) {
  console.log('Service Worker on line!');

}, function(err) {
  console.log('Oops, Service Worker installation failed!');

});

event.waitUntil

self.addEventListener('push', function(event) {
  console.log('Received a push message', event);

  var title = 'Yay a message.';
  var body = 'We have received a push message.';
  var icon = '/images/icon-192x192.png';
  var tag = 'simple-push-demo-notification-tag';

  event.waitUntil(
    self.registration.showNotification(title, {
      body: body,
      icon: icon,
      tag: tag
    })
  );
});

Inside the SW script

// The SW will be shutdown when not in use to save memory,
// be aware that any global state is likely to disappear

console.log("SW startup");

self.addEventListener('install', function(event) {
  console.log("SW installed");
});

self.addEventListener('activate', function(event) {
  console.log("SW activated");
});

self.addEventListener('fetch', function(event) {
  console.log("Caught a fetch!");
  event.respondWith(new Response("Hello world!"));
});

importScripts

importscripts("my-script-file.js");

// the rest of the serviceworker.js, handling fetch, push, etc...

Event Handling:
fetch / push / sync / messages

self.addEventListener('fetch', function(event) {
  event.respondWith(
    caches.match(event.request)
      .then(response => {
        const networkResponse = fetch(event.request)
          .then(fetchResult => {
            cache.put(event.request, fetchResult.clone());
            return fetchResult;
          });

        return response || networkResponse;
      })
  );
});

cache management

the offline cookbook

 

jakearchibald.com/2014/offline-cookbook

cache-first

self.addEventListener('fetch', function(event) {
  event.respondWith(
    caches.match(event.request)
      .then(response => response || fetch(event.request))
  );
});

network-first

self.addEventListener('fetch', function(event) {
  event.respondWith(
    fetch(event.request)
      .catch(ex => caches.match(event.request))
  );
});

bringing out the big guns

self.addEventListener('fetch', function(event) {
  event.respondWith(
    caches.match(event.request)
      .then(response => {
        const networkResponse = fetch(event.request)
          .then(fetchResult => {
            cache.put(event.request, fetchResult.clone());
            return fetchResult;
          });

        return response || networkResponse;
      })
  );
});

Synthetic Responses

self.addEventListener('fetch', function(event) {
  if (event.request.url.match(/hello/i)) {
    event.respondWith(
      new Response("Hello world!")
    );
  }
});

...and so much more!
 

Server push emulation, appcache polyfills, JS transpiling and on-demand feature polyfilling, webserver-in-the-client, differential resource updates...

Support?

Chrome, Firefox, Opera, Samsung Internet, Edge...

Constantly evolving standard

NOT just for offline webapps

Lie-fi: When you are supposed to be online, but not.
Downtime: Maintenance, downtime, zombie apocalypse.
Performance: Any byte not downloaded is a byte saved.

...or Bandwidth caps:

But we need your help!

Service workers aren't a magic wand:

"With ServiceWorker we gave up trying to solve offline, and gave developers the moving parts to go solve it themselves."

Thank you!

GET IN TOUCH!
 

PWA Joburg

By Szmozsánszky István

PWA Joburg

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