Stencil 101: Introduction to a Web Components library like no other

A presentation at sthlm.js in February 2020 in Stockholm, Sweden by Horacio Gonzalez

Slide 1

Stencil 101 Introduction to a web components library like no other Horacio Gonzalez @LostInBrittany

Slide 2

Who are we? Introducing myself and introducing OVH OVHcloud

Slide 3

Horacio Gonzalez @LostInBrittany Spaniard lost in Brittany, developer, dreamer and all-around geek Flutter

Slide 4

OVHcloud: A Global Leader 200k Private cloud VMs running 1 Dedicated IaaS Europe 30 Datacenters Own 20Tbps Hosting capacity : 1.3M Physical Servers 360k Servers already deployed Netwok with 35 PoPs

1.3M Customers in 138 Countries

Slide 5

OVHcloud: Our solutions Cloud Web Hosting Mobile Hosting Telecom VPS Containers ▪ Dedicated Server Domain names VoIP Public Cloud Compute ▪ Data Storage Email SMS/Fax Private Cloud ▪ Network and Database CDN Virtual desktop Serveur dédié Security Object Storage Web hosting Cloud Storage Over the Box ▪ Licences Cloud Desktop Securities MS Oﬃce Hybrid Cloud Messaging MS solutions

Slide 6

The 3 minutes context What the heck are web component?

Slide 7

Web Components Web standard W3C

Slide 8

Web Components Available in all modern browsers: Firefox, Safari, Chrome

Slide 9

Web Components Create your own HTML tags Encapsulating look and behavior

Slide 10

Web Components Fully interoperable With other web components, with any framework

Slide 11

Web Components CUSTOM ELEMENTS SHADOW DOM TEMPLATES

Slide 12

Custom Element To define your own HTML tag <body> … <script> window.customElements.define(‘my-element’, class extends HTMLElement {…}); </script> <my-element></my-element> </body>

Slide 13

Shadow DOM To encapsulate subtree and style in an element <button>Hello, world!</button> <script> var host = document.querySelector(‘button’); const shadowRoot = host.attachShadow({mode:’open’}); shadowRoot.textContent = ‘こんにちは、影の世界!’; </script>

Slide 14

Template To have clonable document template <template id=”mytemplate”> <img src=”” alt=”great image”> <div class=”comment”></div> </template> var t = document.querySelector(‘#mytemplate’); // Populate the src at runtime. t.content.querySelector(‘img’).src = ‘logo.png’; var clone = document.importNode(t.content, true); document.body.appendChild(clone);

Slide 15

But in fact, it’s just an element… ● ● ● ● Attributes Properties Methods Events

Slide 16

Aren’t the multiple Web Components libs a sign of failure? If the standard worked, people would use Vanilla, wouldn’t them?

Slide 17

Web component standard is low level At it should be!

Slide 18

Standard == basic bricks Standard exposes an API to: ○ Define elements ○ Encapsulate DOM

Slide 19

Libraries are helpers They give you higher-level primitives

Slide 20

Different high-level primitives Each one tailored to a use

Slide 21

Sharing the same base High-performant, low-level, in-the-platform web components standard

Slide 22

Libraries aren’t a failure of standard They happen by design

Slide 23

Stencil Powering Ionic 4+

Slide 24

Not another library A Web Component toolchain

Slide 25

A mature technology Ionic 4 released on year ago, powered by Stencil!

Slide 26

A build time tool To generate standard web components

Slide 27

Fully featured ● Web Component-based ● Component pre-rendering ● Asynchronous rendering pipeline ● Simple component lazy-loading ● TypeScript support ● JSX support ● Reactive Data Binding ● Dependency-free components

Slide 28

And the cherry on the cake Server-Side Rendering

Slide 29

Stencil leverages the web platform Working with the web, not against it

Slide 30

The Stencil story A company tired of putting good code in the bin

Slide 31

Once upon a time there was a fight Between native apps and web app on mobile

Slide 32

A quest to the perfect solution Hybrid apps, leveraging on web technologies

Slide 33

A company wanted to do it well The perfect technology for mobile web and hybrid apps

Slide 34

The time is 2013 So what technology would you use?

Slide 35

Really soon after launch… Hey folks, we are killing AngularJS!

Slide 36

What did Ionic people do? Let’s put everything in the trash bin and begin anew

Slide 37

But timed have changed… In 2013 Angular JS was the prom queen

Slide 38

Times have changed… In 2017 Angular is only one more in the clique

Slide 39

Angular limits adoption of Ionic Devs and companies are very vocal about JS Frameworks

Slide 40

What did Ionic people do? Let’s put everything in the trash bin and begin anew… But on which framework?

Slide 41

What about web components? A nice solution for Ionic problems: Any framework, even no framework at all!

Slide 42

But what Web Component library? SkateJS There were so many of them!

Slide 43

Let’s do something different A fully featured web component toolchain With all the bells and whistles!

Slide 44

Ionic rewrote all their code again Ionic 4 is fully based on Ionic

Slide 45

Now Ionic works on any framework Or without framework at all

Slide 46

And we have Stencil To use it in any of our projects

Slide 47

Hey dude, enough stories! We are here to see some code!

Slide 48

Hands on Stencil Simply use npm init npm init stencil Choose the type of project to start ? Pick a starter › - Use arrow-keys. Return to submit. ❯ ionic-pwa Everything you need to build fast, production ready PWAs app Minimal starter for building a Stencil app or website component Collection of web components that can be used anywhere Updating Stencil

Slide 49

Hands on Stencil And the project is initialized in some seconds! ✔ Pick a starter › component ✔ Project name › sthlm-j ✔ All setup in 17 ms $ npm start Starts the development server. $ npm run build Builds your components/app in production mode. $ npm test Starts the test runner. We suggest that you begin by typing: $ cd sthlm-js $ npm start Happy coding! 🎈

Slide 50

Starting the development server npm start

Slide 51

Let’s look at the code

Slide 52

Some concepts import { Component, Prop, h } from ‘@stencil/core’; import { format } from ‘../../utils/utils’; @Component({ tag: ‘my-component’, styleUrl: ‘my-component.css’, shadow: true }) export class MyComponent { @Prop() first: string; Decorators

Slide 53

Some concepts @Prop() first: string; @Prop() middle: string; @Prop() last: string; @State() nickname: string; Properties and States

Slide 54

Some concepts render() { return <div>Hello, World! I’m {this.getText()}</div>; } Asynchronous rendering using JSX

Slide 55

Some concepts @Prop() value: number; @Watch(value) valueChanged(newValue: boolean, oldValue: boolean) { console.log(The new value is ${newValue}, it was ${oldValue} before); } Watch

Slide 56

Some concepts @Event() actionCompleted: EventEmitter; someAction(message: String) { this.actionCompleted.emit(message); } Emitting events @Listen(‘actionCompleted’) actionCompletedHandler(event: CustomEvent) { console.log(‘Received the custom actionCompleted event: ‘, event.detail); } Listening to events

Slide 57

Some concepts @Method() async sayHello() { this.hello = true; } render() { return ( <Host> <h2>{ this.hello ? Hello sthlm.js : ”}</h2> </Host> ); } Asynchronous public methods