Web components are a set of web platform APIs that allow you to create reusable custom elements with their functionality encapsulated away from the rest of your code. They provide a way to build custom, reusable, and encapsulated components in web applications, promoting modularity and reusability.
There are four main technologies that make up web components:
-
Custom Elements:
These allow developers to define their custom HTML elements, with their own behavior and properties. Custom elements are created using JavaScript by extending the
HTMLElement
class and registering the new element usingcustomElements
.define(). - Shadow DOM (Document Object Model): Shadow DOM enables the encapsulation of styles, markup, and behavior for a component. It allows you to attach a hidden DOM tree to an element, keeping the functionality and styling of the component isolated from the rest of the page.
- HTML Templates: HTML templates provide a way to declare fragments of markup that can be cloned and inserted into the DOM as needed. Templates are not rendered until they are explicitly cloned and used.
- HTML Imports (deprecated in favor of ES modules): HTML Imports were a way to include and reuse HTML documents in other HTML documents. However, they have been deprecated in favor of ES modules and the native JavaScript module system.
class MyCustomElement extends HTMLElement {
constructor() {
super();
// Create a shadow DOM for this custom element
const shadow = this.attachShadow({ mode: 'open' });
// Create a paragraph element
const paragraph = document.createElement('p');
paragraph.textContent = 'This is a custom element!';
// Append the paragraph to the shadow DOM
shadow.appendChild(paragraph);
}
}
// Register the custom element with the browser
customElements.define('my-custom-element', MyCustomElement);
Then, in HTML:
<my-custom-element></my-custom-element>
Web components provide a way to build reusable components that can be used across different frameworks or applications. They encourage modularity, encapsulation, and maintainability by allowing developers to create their own custom elements with well-defined functionality, reducing code duplication and promoting a more structured approach to web development.