kgreen kgreen - 1 year ago 79
Javascript Question

Unable to create custom element when extending built-in element in Chrome 54

I'm unable to create a custom element when extending from a built-in element in Chrome 54.

To my knowledge this feature has shipped. Is there something I am missing? Perhaps this portion of the v1 spec is still in flux.

<super-element>Super Element</super-element>
<button is="super-button">Super Button</button>

customElements.define('super-element', class extends HTMLElement {
constructor() {
console.log('Super Element');

customElements.define('super-button', class extends HTMLButtonElement {
constructor() {
console.log('Super Button');
}, {extends: 'button'});

// Output: Super Element


Answer Source

Perhaps this portion of the v1 spec is still in flux.


Customized built-in elements are not implemented yet in Blink, the Chrome & Opera HTML rendering engine.

Look at the "Launch" and "Implement" bugs in Chromium project's tracker.

See also SO answer here for a workaround.

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