JavaScript Custom Elements Registering New Elements
Example
Defines an <initially-hidden> custom element which hides its contents until a specified number of seconds have elapsed.
const InitiallyHiddenElement = document.registerElement('initially-hidden', class extends HTMLElement {
createdCallback() {
this.revealTimeoutId = null;
}
attachedCallback() {
const seconds = Number(this.getAttribute('for'));
this.style.display = 'none';
this.revealTimeoutId = setTimeout(() => {
this.style.display = 'block';
}, seconds * 1000);
}
detachedCallback() {
if (this.revealTimeoutId) {
clearTimeout(this.revealTimeoutId);
this.revealTimeoutId = null;
}
}
});
<initially-hidden for="2">Hello</initially-hidden>
<initially-hidden for="5">World</initially-hidden>
