HTML Web Components - Speaker Deck

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@cferdinandi GoMakeThings.com Welcome to the light side WEB COMPONENTS HTML

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The Uncanny Valley of Web Components

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The Grain of the Web

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Chris Ferdinandi GoMakeThings.com

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The 1st Web Component

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Web Components https://wallpaperaccess.com

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https://www.wallpaperflare.com Every Website

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this.innerHTML = ` Clicked 0 Times `;

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// Create the Shadow DOM this.root = this.attachShadow({ mode: 'closed' }); // Inject HTML into it this.root.innerHTML = ` Clicked 0 Times `;

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// Add styles to the Shadow DOM let stylesheet = new CSSStyleSheet(); stylesheet.replaceSync( `button { background-color: #08c; border: 1px solid #08c; color: #fff; }` ); this.root.adoptedStyleSheets = [stylesheet];

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but web native?

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Reactivity

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Reactivity DOM Diffing

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Reactivity DOM Diffing Single File Components

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but web native?

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The Grain of the Web

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Start End

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Start End 1 A new approach…

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Start End 1 A new approach… Tips & Tricks 2

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Start End 1 A new approach… Tips & Tricks 2 3 Examples

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A new approach… (that’s kind of old-school) 1

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Try not to bring React’s mindset with you… Do you really need to invent an entirely new component from scratch? Or can you use HTML up until it reaches its limit and then enhance the markup? — Jeremy Keith https://adactio.com/journal/20618

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Merlin

Beard & books

Ursula

Really wants to sing

Radagast

Prefers dogs over people

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Merlin

Beard & books

Ursula

Really wants to sing

Radagast

Prefers dogs over people

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Merlin

Beard & books

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BIG benefits

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Easier to Write

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this.innerHTML = ` Clicked 0 Times `; YUCK!

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new Accordion('#wizards');

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Better Performance

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=*(

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// Wizard info new Accordion('#wizards'); // FAQs new Accordion('#faq', { heading: 'h3', autoclose: true }); 👋 Bye!

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Tips & Tricks 2

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Clicked 0 Times

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customElements.define( 'count-up', class extends HTMLElement { // Instantiate component constructor () { // ... } } );

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constructor () { // Always run first super(); // Your code... }

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Encapsulation

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constructor () { // Always run first super(); // Define properties this.count = 0; this.btn = this.querySelector('button'); }

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count-up button { background-color: #08c; border: 1px solid #08c; color: #fff; }

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/* JS is loaded! */ count-up:defined { /* ... */ } /* No JS yet */ count-up:not(:defined) { /* ... */ }

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🎉 Event Handling

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constructor () { // ...   // Define properties this.count = 0; this.btn = this.querySelector('button'); // Listen for click events this.btn.addEventListener('click', this); }

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// Handle click events handleEvent (event) { this.count++; this.btn.textContent = `Clicked ${this.count} Times`; }

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// Handle events handleEvent (event) { this[`on${event.type}`](event); } // Handle click events onclick (event) { console.log('clicked!'); }

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⚙ Declarative Settings

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Clicked 42 Times

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constructor () { // Always run first super(); // Define properties let start = this.getAttribute('start'); this.count = parseFloat(start) || 0; this.btn = this.querySelector('button'); }

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Clicked 0 Times Clicked 42 Times

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Attribute Reactivity

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Attribute Reactivity

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Clicked 0 Times

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// Define the attributes to observe static observedAttributes = ['pause'];

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// Runs when the value of // an attribute is changed on the component attributeChangedCallback (name, oldVal, newVal) { this.btn.removeEventListener('click', this); } // Define the attributes to observe static observedAttributes = ['pause'];

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attributeChangedCallback (name, oldVal, newVal) { if (newVal === null) { this.btn.addEventListener('click', this); } else { this.btn.removeEventListener('click', this); } }

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Examples 3

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Now you see me!

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Now you see me!

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customElements.define( 'show-hide', class extends HTMLElement { // … } );

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// Instantiate the component constructor () { // Run first super(); // Define properties this.btn = this.querySelector('button'); this.content = this.btn.nextElementSibling; }

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constructor () { // ... // Define properties this.btn = this.querySelector('button'); this.content = this.btn.nextElementSibling; // Set initial UI this.btn.setAttribute('aria-expanded', false); this.content.setAttribute('hidden', ''); }

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Now you see me!

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constructor () { // ... // Set initial UI this.btn.setAttribute('aria-expanded', false); this.content.setAttribute('hidden', ''); // Listen for click events this.btn.addEventListener('click', this); }

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handleEvent (event) { // If the content is expanded, hide it // Otherwise, show it if (this.btn.getAttribute('aria-expanded') === 'true') { // ... } else { // ... } }

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handleEvent (event) { // If the content is expanded, hide it // Otherwise, show it if (this.btn.getAttribute('aria-expanded') === 'true') { this.btn.setAttribute('aria-expanded', false); this.content.setAttribute('hidden', ''); } else { this.btn.setAttribute('aria-expanded', true); this.content.removeAttribute('hidden'); } }

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show-hide button { background-color: #08c; border: 1px solid #08c; color: #fff; } show-hide button[aria-expanded="true"] { background-color: #343d4d; border: 1px solid #343d4d; }