Web Components

 

Use it or Lose it?

Sara HARKOUSSE

Duchess France

Paris, 17 Mai 2017

http://vignette2.wikia.nocookie.net/weirdcommunity/images/a/a2/Rainbow-flow-abstract-backgrounds-for-powerpoint.jpg/revision/latest?cb=20130603085532​​

SARA HARKOUSSE

@Sara_harkousse

 

 

Tech Lead, front-end Web developer at Dassault Systèmes

3D design & PLM software

 

"Duchess France" contributor & 3DS advocate at "Elles Bougent"

 

 

About me

#DuchessFrance2017

Motivation

  • Modular architecture

Filterable Product Table

Search Bar

Product Table

Product Row

Product Category Row

https://facebook.github.io/react/docs/thinking-in-react.html

#DuchessFrance2017 #webcomponents @Sara_harkousse

Angular 4.0 Component

import { Component } from '@angular/core';

@Component({
  selector: 'my-app',
  template: `<h1>Hello {{name}}</h1>`
})

export class AppComponent { name = 'Angular'; }

<my-app><h1>Hello Angular</h1></my-app>

https://embed.plnkr.co/?show=preview&show=app%2Fapp.component.ts

#DuchessFrance2017 #webcomponents @Sara_harkousse

Ember 2.12.0 Component

<article class="blog-post">
  <h1>{{title}}</h1>
  <p>{{yield}}</p>
  <p>Edit title: {{input type="text" value=title}}</p>
</article>
{{#each model as |post|}}
  {{#blog-post title=post.title}}
    {{post.body}}
  {{/blog-post}}
{{/each}}

https://guides.emberjs.com/v2.12.0/components/defining-a-component/

Polymer 2.0 Element

  // Define the class for a new element called custom-element
  class CustomElement extends Polymer.Element {
    static get is() { return "custom-element"; }
    constructor() {
        super();
        this.textContent = "I'm a custom-element.";
      }
  }
  // Register the new element with the browser
  customElements.define(CustomElement.is, CustomElement);
<custom-element></custom-element>

http://plnkr.co/edit/PaCt2M?p=preview

Frameworks make it hard to get along

#DuchessFrance2017 #webcomponents @Sara_harkousse

#DuchessFrance2017 #webcomponents @Sara_harkousse

Browser support

https://www.webcomponents.org/

  • use webcomponents.js

Refresher on web components

Web components are a set of web platform APIs that allow you to create new custom, reusable, encapsulated HTML tags to use in web apps.”

#DuchessFrance2017 #webcomponents @Sara_harkousse

https://www.webcomponents.org/

Refresher on web components

  • HTML Template Tag

  • HTML Imports

  • Custom Elements

  • Shadow DOM

#DuchessFrance2017 #webcomponents @Sara_harkousse

HTML Template Tag

  <template id="template">
    <div id="container">
      <img class="webcomponents" src="https://webcomponents/imgs/webcomponents-logo.svg">
    </div>
  </template>

https://jsfiddle.net/sara_harkousse/rnu8zc0c/

#DuchessFrance2017 #webcomponents @Sara_harkousse

HTML Template Tag Usage

var template = document.querySelector('#template');
var clone = document.importNode(template.content, true);
var host = document.querySelector('#host');
host.appendChild(clone);

https://jsfiddle.net/sara_harkousse/rnu8zc0c/

#DuchessFrance2017 #webcomponents @Sara_harkousse

HTML Template Tag

  • A way to add inert DOM elements to your document

  • Not something that's going to revolutionize your apps

  • No two-way data binding, no binding at all

#DuchessFrance2017 #webcomponents @Sara_harkousse

HTML Imports

 <link rel="import" href="/imports/productRow.html"> 
 <script src="js/productRow.js"></script> 
 <template> 
    <!-- content-->
 <template>

#DuchessFrance2017 #webcomponents @Sara_harkousse

How to get my component?

var link = document.querySelector('link[rel="import"]');
var content = link.import;

// Grab DOM from productRow.html's document.
var el = content.querySelector('.productRow');
document.body.appendChild(el.cloneNode(true));

#DuchessFrance2017 #webcomponents @Sara_harkousse

Hammering our server

  • Each one of the HTML imports is another XMLHttpRequest

#DuchessFrance2017 #webcomponents @Sara_harkousse

Build tools for HTML Import

  • e.g. Vulcanizr (turns all imports into one import)

#DuchessFrance2017 #webcomponents @Sara_harkousse

HTML Import requires a polyfill

  • ES6 module?

https://www.webcomponents.org/

#DuchessFrance2017 #webcomponents @Sara_harkousse

Shadow DOM

  • A tiny document

  • exists inside of a host element

#DuchessFrance2017 #webcomponents @Sara_harkousse

Key concepts

  • Isolated DOM

  • Scoped CSS

#DuchessFrance2017 #webcomponents @Sara_harkousse

Shadow DOM requires a polyfill

  • Hard to polyfill

#DuchessFrance2017 #webcomponents @Sara_harkousse

Use/Don't use

Shadow DOM?

callback() {
    // Use it
    this.root = this.attachShadow({mode: 'open'});

    var template = document.querySelector('#template');
    var clone = document.importNode(template.content, true);
    this.root.appendChild(clone);
}

callback() {
    // Don't Use it
    this.root = this;

    var template = document.querySelector('#template');
    var clone = document.importNode(template.content, true);
    this.root.appendChild(clone);
}

#DuchessFrance2017 #webcomponents @Sara_harkousse

Use/Don't use

Shadow DOM?

/* Use it */
:host {
    color: red;
}

/* Don't use it */
custom-component {
    color: red;
}

#DuchessFrance2017 #webcomponents @Sara_harkousse

Use AND Don't use

Shadow DOM

if (shadowflag){
    this.root = this.attachShadow({mode: 'open'});
} else {
    this.root = this;
}
custom-component, :host {
    color: red;
}

#DuchessFrance2017 #webcomponents @Sara_harkousse

Custom Elements

class CustomButton extends HTMLElement {...}
window.customElements.define('custom-button', CustomButton);

<custom-button></custom-button>

  • Acts like a div

#DuchessFrance2017 #webcomponents @Sara_harkousse

Custom Elements

class CustomButton extends HTMLButtonElement {...}
window.customElements.define('custom-button', CustomButton, {extends: 'button'});
<button is="custom-button" disabled>My button!</button>

  • Acts like a real button

#DuchessFrance2017 #webcomponents @Sara_harkousse

Custom Elements ES6 Class

class custom-component extends HTMLElement {
  constructor() {
    super(); // always call super() first in the ctor.
    ...
  }
  connectedCallback() {
    ...
  }
  disconnectedCallback() {
    ...
  }
  attributeChangedCallback(attrName, oldVal, newVal) {
    ...
  }

}

#DuchessFrance2017 #webcomponents @Sara_harkousse

Component example

 Bootstrap Progress Bar

<div class="progress">
  <div class="progress-bar" style="width: 60%;">
    60%
  </div>
</div>

#DuchessFrance2017 #webcomponents @Sara_harkousse

window.customElements.define('progress-bar', ProgressBar);
// Use
<progress-bar></progress-bar>

Component example

#DuchessFrance2017 #webcomponents @Sara_harkousse

https://jsfiddle.net/sara_harkousse/kwwe75yy/

class ProgressBar extends HTMLElement { 
	
	constructor() { 
		super(); // always call super() first in the ctor.
		
		this.shadow = this.attachShadow({mode: 'open'});
		this._complete = 0;				
	}
	
	get complete() {
		return this._complete;
	}
	
	set complete(val) {
		this.setAttribute('complete', val);
	}	
	
	static get observedAttributes() {
		return ['complete'];
	}	

	attributeChangedCallback(name, oldval, newval) {
		var innerBar = this.shadow.querySelector('.progress-bar-inner');
		switch(name) {
			case 'complete':
				this._complete =  parseInt(newval, 10) || 0;
				innerBar.style.width = this.complete + '%';
				innerBar.innerHTML = this.complete + '%';
		}
	}
	
	connectedCallback() {
		var template = `<div class="progress-bar">
				    <div class="progress-bar-inner">${this.complete}%</div>
				</div>`; 
		this.shadow.innerHTML = template;
	}
}

Components on a page

<!doctype html>
<html lang="en">

    <head>
        <link rel="import" href="/imports/productRow.html">
    </head>

    <body>
        <custom-navbar style="compact"></custom-navbar>
        <custom-toolbar style="full"></custom-toolbar>
        <custom-pagecontent>
            <custom-item attr="val"></custom-item>
            <custom-input attr="val"></custom-input>
            <progress-bar></progress-bar>
        </custom-pagecontent>

        <script>
            document.querySelector('progress-bar').addEventListener(
                'customevent', function () {
                    // do something
                 }
            });
        </script>
    </body>

</html>

#DuchessFrance2017 #webcomponents @Sara_harkousse

Takeaway

You will understand some of the design decisions of major frameworks if you learn about custom elements

#DuchessFrance2017 #webcomponents @Sara_harkousse

Takeaway

Who is using web components?

#DuchessFrance2017 #webcomponents @Sara_harkousse

Takeaway

GitHub

Mozilla VR

Google

#DuchessFrance2017 #webcomponents @Sara_harkousse

Thanks for listening!

Follow for slides

@Sara_harkousse

#DuchessFrance2017 #webcomponents

http://slides.com/sara_harkousse/web-components-talk-2#/

Web Components: Use it or Lose it?

By sara_harkousse

Made with Slides.com

Web Components: Use it or Lose it?

Web components are a tale of four w3c specifications. They are a hot topic now. We’ve all seen big headlines, for instance, “The Web Components revolution”, “Web Components are a game changer”, “A Tectonic Shift for Web Development”, … and so many others. They are certainly exciting and promising, nevertheless, there are some factors holding them back such as performance issues and lack of browser support. Some features seems to be more hassle than they’re worth. In this talk you’ll examine web components from a pragmatic stand point. So if you want to start using web components in production, come to learn what features can you use today. Actually, despite the still short browser support, some of web components features seems to be the best choice to start with . The assessment you’ll learn is the reflection of my personal research and work on my spare time and also feedbacks from my co-workers.

  • 585

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