HTML Custom Elements are a key feature of Web Components, allowing developers to create new, reusable HTML tags with custom functionality. They extend the HTML vocabulary, enabling more semantic and modular web development.
To create a custom element, use JavaScript to define a new class that extends HTMLElement
. Then, register it with the customElements.define()
method.
class MyElement extends HTMLElement {
constructor() {
super();
this.innerHTML = 'Hello from MyElement!';
}
}
customElements.define('my-element', MyElement);
Once defined, custom elements can be used in HTML just like built-in elements:
<my-element></my-element>
Custom elements can implement lifecycle callbacks to hook into key moments:
connectedCallback()
: Invoked when the element is added to the DOMdisconnectedCallback()
: Called when the element is removed from the DOMattributeChangedCallback()
: Triggered when an observed attribute changesYou can also extend existing HTML elements to create customized versions:
class FancyButton extends HTMLButtonElement {
constructor() {
super();
this.style.backgroundColor = 'gold';
}
}
customElements.define('fancy-button', FancyButton, { extends: 'button' });
Use the extended element with the is
attribute:
<button is="fancy-button">Click me!</button>
<my-element>
)Custom Elements are widely supported in modern browsers. However, for older browsers, consider using a polyfill to ensure compatibility.
Custom Elements work seamlessly with other web technologies:
By mastering HTML Custom Elements, developers can create more maintainable, reusable, and expressive code, enhancing the overall structure and functionality of web applications.