Hello World Example

Rafał Lorenz edited this page May 17, 2017 · 4 revisions

For example to create HelloWorld component and use it in your index.html file as follow:

<hello-world who="Unicorn"></hello-world>

You could setup component like shown below:

  1. Template file hello-world.html
<h1>Hello<span id="who"></span>!</h1>
  1. Javascript file hello-world.js
import { WebComponent } from 'web-component'

@WebComponent('hello-world', {
  template: require('./hello-world.html'),
  shadowDOM: true
export class HelloWorld extends HTMLElement {
  constructor() {
    this._who = null; //this property is bind to element attribute becouse of observedAttributes

  static get observedAttributes() {
    return ['who'];

  // Only called for the who attributes due to observedAttributes
  attributeChangedCallback(name, oldValue, newValue) {
    //this._who = newValue; this is handled by WebComponent decorator

  connectedCallback() {
    // this is handled by WebComponent decorator
    // if (this.hasAttribute('who')) {
    //   this._who = this.getAttribute('who');
    // }

  // Decorator creates setter/getter methods for observed attributes
  //we do not have to do this

  // get who() {
  //   return this._who;
  // }

  // set who(v) {
  //   this.setAttribute("who", v);
  // }

  _updateRendering() {
    this.shadowRoot.querySelector('#who').textContent = `, ${this._who}`;
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