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Custom Elements

Unveiling Custom Elements

Welcome back! Let's journey into the realm of Custom Elements, a revolutionary way to build reusable and encapsulated components in our web applications.

What are Custom Elements?

Custom Elements empower you to create your own HTML elements that extend the browser's built-in elements with unique functionality and appearance.

The CustomElementRegistry Interface

const customElementRegistry = document.createElementRegistry();

The CustomElementRegistry interface grants you access to all registered custom elements in the browser.

Creating Custom Elements

class MyCustomElement extends HTMLElement { ... }

Extend the HTMLElement class to define your custom element's behavior and appearance.

Defining the Element's Template

<template id="my-element-template"><p>Hello, world!</p></template>

Use a template element to encapsulate the custom element's HTML structure.

Defining the Element's Behavior

class MyCustomElement extends HTMLElement { connectedCallback() { ... } }

Implement lifecycle callbacks (like connectedCallback) to define the element's behavior upon insertion into the DOM.

The Lifecycle of a Custom Element

  • constructor: Invoked when the element is created.
  • connectedCallback: Called when the element is inserted into the DOM.
  • disconnectedCallback: Called when the element is removed from the DOM.
  • Attaching Event Listeners

    myCustomElement.addEventListener('click', () => { ... });

    Attach event listeners to custom elements to respond to user interactions.

    Customizing the Shadow DOM

    Custom Elements create a Shadow DOM, providing encapsulation and isolation of the element's internal structure.

    Styling Custom Elements

    my-custom-element { background-color: red; }

    Apply styles directly to custom elements using CSS.

    Slot Elements

    <my-custom-element><slot><p>This is a slot.</p></slot></my-custom-element>

    Slot elements allow you to insert content from the parent element into the custom element.

    Using Custom Elements in HTML


    Just like built-in elements, you can use custom elements in your HTML markup.

    The Shadow DOM in Depth

    Explore the Shadow DOM's role in encapsulation, performance optimization, and security.

    Benefits of Using Custom Elements

  • Reusable Components
  • Encapsulation
  • Improved Readability
  • Extensibility
  • Next Up: HTML Templates

    Discover the power of HTML templates for dynamic and reusable content manipulation. Follow us for more exciting content! #HTMLTemplates #WebComponents