Maxim Salnikov

@webmaxru

Getting started with

Progressive Web Apps

Progressive Web App — a modern definition

and how to get started

Maxim Salnikov

@webmaxru

  • PWA Summit co-organizer

  • PWA Oslo / PWA London meetups organizer

  • Google Dev Expert in Web Tech / Capabilities & Installability

Developer Audience Lead at Microsoft

PWA chapter of Web Almanac 2021

https://almanac.httparchive.org/en/2021/pwa​

Web as an app platform

  • Historically depends on the "connection status"

  • Historically limited to work in the browser, not a platform context

  • Evergreen browsers

  • Versatile language

  • Performant JS engines

  • Excellent tooling

  • Huge community

https://infrequently.org/2015/06/progressive-apps-escaping-tabs-without-losing-our-soul/

🎂

What is PWA at all?

Progressive Web Apps are web apps that use emerging web browser APIs and features along with traditional progressive enhancement strategy

https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps

to bring a native app-like user experience to cross-platform web applications.

A useful design pattern, not a formalized standard.

works everywhere*

* but not everything**

natively

** use progressive enhancement strategy

Native-like experiences?

Smart networking + Offline

Proper app experience

Staying notified

Background tasks

whatpwacando.today

Capabilities

Offline-readyness

Installability

Name, icons, start URL

...

...

=

+

Service worker

Web app manifest

Served via HTTPS

Proper offline-ready web app

  • App itself

  • Online runtime data

  • Offline runtime data

  • Connection failures

  • Updates

  • Platform features

  • Always available

  • Thoughtfully collected

  • Safely preserved

  • Do not break the flow

  • Both explicit and implicit

  • For the win!

While keeping its web nature!

Let's build an App shell

My App

  • Define assets

  • Put in the cache

  • Serve from the cache

  • Manage versions

}

Service worker

Service worker

Service

worker

OS

Browser

Internet

App

Event

Event

Event

Event

  • Message app

  • Launch the browser and app

  • Show notification

  • Run custom code

Message

Own service worker

self.addEventListener('install', event => {
    // Use Cache API to cache html/js/css
})

self.addEventListener('activate', event => {
    // Clean the cache from the obsolete versions
})

self.addEventListener('fetch', event => {
    // Serve assets from cache or network
})

handmade-service-worker.js

Lots of things to care about...

Redirects?

Fallbacks?

Opaque response?

Versioning?

Cache invalidation?

Spec updates?

Cache storage space?

Variable asset names?

Feature detection?

Minimal required cache update?

Caching strategies?

Routing?

Fine-grained settings?

Kill switch?

I see the old version!!!

https://developers.google.com/web/tools/workbox/

  • Define assets

  • Put in the cache

  • Serve from the cache

  • Manage versions

}

Is there a helper?

While having our own service worker

aka.ms/workbox6

  • Video and slides

  • Source code

Reach

"Nativeness"

Native

Web

https://web.dev/what-are-pwas/

Web applications can reach anyone, anywhere, on any device with a single codebase.

Nativeness = Number & depth of integrations with the platform

Installability & beyond

Integration points available

  • Installation & run

  • Windowing

  • Outbound integrations

  • Inbound integrations

  • Notifications

  • Background tasks

  • Access to hardware

Installation & run

  • Installation

  • Uninstallation

  • Run on user login

  • Shortcuts

  • Launch mode

Installation & run

  • Installation

  • Uninstallation

  • Run on user login

  • Shortcuts

  • Launch mode

Web App Manifest

Service Worker with "fetch"

{

{
  "name": "BPM Techno",
  "short_name": "BPM Techno Counter",
  "start_url": "?utm_source=homescreen",
  "display": "standalone",
  "background_color": "#fff",
  "description": "A free online BPM counter",
  "icons": [{
    "src": "images/touch/48x48.png",
    "sizes": "48x48",
    "type": "image/png"
  }]
}

site.webmanifest

https://web.dev/install-criteria/

Installation & run

  • Installation

  • Uninstallation

  • Run on user login

  • Shortcuts

  • Launch mode

"shortcuts": [
  {
    "name": "Upload MP3 File",
    "short_name": "Upload MP3r",
    "description": "Count BPM of the uploaded file",
    "url": "/upload-mp3?utm_source=homescreen",
    "icons": [{ "src": "/icon-mp3.png", "sizes": "192x192" }]
  }
]

site.webmanifest

https://web.dev/app-shortcuts/

Installation & run

  • Installation

  • Uninstallation

  • Run on user login

  • Shortcuts

  • Launch mode

"launch_handler": {
  "route_to": "new-client" | "existing-client" |
    "auto",
  "navigate_existing_client": "always" | "never",
}

site.webmanifest

https://github.com/WICG/sw-launch/blob/main/launch_handler.md​

launchQueue.setConsumer(launchParams => {
  const url = launchParams.targetURL;
});

main.js

Windowing

  • Main window mode

  • Title bar options

  • Status bar options

  • Tabbed experience

Windowing

  • Main window mode

  • Title bar options

  • Tabbed experience

{
  "display": "fullscreen" | "standalone" |
    "minimal-ui" | "browser",
  "display_override": ["window-control-overlay",
    "minimal-ui"],
}

site.webmanifest

https://github.com/WICG/display-override/blob/main/explainer.md

Windowing

  • Main window mode

  • Title bar options

  • Tabbed experience

titlebar-area-x
titlebar-area-y
titlebar-area-width
titlebar-area-height

CSS Variables

https://github.com/WICG/window-controls-overlay/blob/main/explainer.md

navigator.windowControlsOverlay.
  getBoundingClientRect()

navigator.windowControlsOverlay.visible

JavaScript API

Windowing

  • Main window mode

  • Title bar options

  • Tabbed experience

https://github.com/w3c/manifest/issues/737​

{
  "display_override": "tabbed"
}

site.webmanifest

PWA Builder & PWA Studio

https://pwabuilder.com

Where to follow?

  • Full-fledged application platform

  • Offline-ready mechanisms are in production

  • Web apps are real apps

  • User experience & security is the key

And this is just the beginning!

Web platform today

Thank you!

Maxim Salnikov

@webmaxru

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