CustomElementRegistry: upgrade() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

The upgrade() method of the CustomElementRegistry interface upgrades all shadow-containing custom elements in a Node subtree, even before they are connected to the main document.

Syntax

js
upgrade(root)

Parameters

root

A Node instance with shadow-containing descendant elements to upgrade. If there are no descendant elements that can be upgraded, no error is thrown.

Return value

None (undefined).

Examples

Taken from the HTML spec:

js
const el = document.createElement("spider-man");

class SpiderMan extends HTMLElement {}
customElements.define("spider-man", SpiderMan);

console.assert(!(el instanceof SpiderMan)); // not yet upgraded

customElements.upgrade(el);
console.assert(el instanceof SpiderMan); // upgraded!

Specifications

Specification
HTML Standard
# dom-customelementregistry-upgrade-dev

Browser compatibility

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