Web Components

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Leo + case + iron

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Another JS Framework?

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State of JS (Interested)

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Why React is so popular?

  • Reusable components
  • Easy to get started
  • Browser support (IE8)
  • Performance

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JSConfUS 2013
Tom Occhino and Jordan Walke: JS Apps at Facebook

Things we accept in React 

  • Compile (Webpack/Babel/Parcel)
  • JSX (htmlFor, className, ...junk)
  • CSS in JS (hashes)
  • Can't use outside React

  hate

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In Jun 2015, I was using SMACSS
Scalable Modular Architecture for CSS
smacss.com

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React: CSS in your JS by Christopher Chedeau

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Answer: CSS in JS

SHADOW DOM

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What is Shadow DOM?

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  • Isolated DOM: A component's DOM is self-contained (e.g. document.querySelector() won't return nodes in the component's shadow DOM).
  • Scoped CSS: CSS defined inside shadow DOM is scoped to it. Style rules don't leak out and page styles don't bleed in.
  • Composition: Design a declarative, markup-based API for your component.
  • Simplifies CSS - Scoped DOM means you can use simple CSS selectors, more generic id/class names, and not worry about naming conflicts.
  • Productivity - Think of apps in chunks of DOM rather than one large (global) page.

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Shadow DOM Tree

Shadow DOM example

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A Guide to Working with Shadow DOM using Selenium

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CSS in JS Libraries 2020

  • Aphrodite
  • Emotion
  • Glamor
  • Glamorous (dead)
  • Fela
  • JSS
  • Linaria
  • Radium
  • Styled components
  • Styletron

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CSS in JS 2020
using Shadow DOM

attachShadow
ShadowRoot

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Shadow DOM
styled-components HACK

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Web Components

HTML Templates

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Custom Elements

Shadow DOM

Custom Element

class WordCount extends HTMLElement {
  constructor() {
    // Always call super first in constructor
    super();

    // Element functionality written in here
  }
}

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Custom Element

class WordCount extends HTMLParagraphElement {
   // ...
}
customElements.define('word-count', WordCount, { extends: 'p' });
<word-count></word-count>

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Custom Elements

Lifecycle callbacks

  • connectedCallback()
     
  • disconnectedCallback()
     
  • adoptedCallback()
    Invoked component is moved to a new document.
     
  • attributeChangedCallback()
    Invoked added, removed, or changed.

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update.onclick = function() {
  // Randomly update square's attributes
  square.setAttribute('l', random(50, 200));
  square.setAttribute('c', `rgb(${random(0, 255)}, ${random(0, 255)}, ${random(0, 255)})`);
};

Shadow DOM

// Create a shadow root
var shadow = this.attachShadow({ mode: 'open' });


// Create some CSS to apply to the shadow dom
var style = document.createElement('style');

style.textContent = `
  .custom {
    color: red
  }
`;

// attach the created elements to the shadow dom
shadow.appendChild(style);

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Shadow DOM example

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HTML Templates

<template id="my-paragraph">
  <p>My paragraph</p>
</template>
let template = document.getElementById('my-paragraph');
let templateContent = template.content;
document.body.appendChild(templateContent);

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Live Code

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Web Components

App Demo

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TODO App Examples

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Convert React into Web Components

Create Web Components using React

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Conclusion

Be aware, that popular languages and libraries get replaced

iframes, table layouts, css float layout, ...

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  • Visual Basic
  • ASP3
  • PHP
  • ActionScript (Flash)
  • Silverlight
  • Ajax
  • XML
  • jQuery
  • GruntJS
  • Gulp
  • AngularJS

References

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Questions?

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Web Components

By Leo Caseiro

Web Components

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