The Case for Custom Elements: Part 1

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JavaScript DOM
The Case for Custom Elements: Part 1 – Dev Channel – Medium by Rod Dodson
Custom Elements:

  • Let you define your own HTML tag with bundled JS behavior
  • Trigger lifecycle callbacks
  • Automatically “upgrade” your tag when inserted in the document
A simple example:
  /* my-element.js */
class MyElement extends HTMLElement {
  // This gets called when the HTML parser sees your tag
  constructor() {
    super(); // always call super() first in the ctor.
    this.msg = 'Hello, World!';
  // Called when your element is inserted in the DOM or
  // immediately after the constructor if it’s already in the DOM
  connectedCallback() {
    this.innerHTML = `<p>${this.msg}</p>`;
// This registers your new tag and associates it with your class
window.customElements.define('my-element', MyElement);
Then you can use in your DOM:
  <script src="my-element.js"></script>