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Window: customElements property

The customElements read-only property of the Window interface returns a reference to the CustomElementRegistry object, which can be used to register new custom elements and get information about previously registered custom elements.

Examples

The most common example you'll see of this property being used is to get access to the CustomElementRegistry.define() method to define and register a new custom element, e.g.:

let customElementRegistry = window.customElements;
customElementRegistry.define("my-custom-element", MyCustomElement);

However, it is usually shortened to something like the following:

customElements.define(
  "element-details",
  class extends HTMLElement {
    constructor() {
      super();
      const template = document.getElementById(
        "element-details-template",
      ).content;
      const shadowRoot = this.attachShadow({ mode: "open" }).appendChild(
        template.cloneNode(true),
      );
    }
  },
);

See our web-components-examples repo for more usage examples.

Specifications

Specification
HTML Standard # dom-window-customelements

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`customElements`	54	79	63	No	41	10.1	54	54	63	41	10.3	6.0

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https://developer.mozilla.org/en-US/docs/Web/API/Window/customElements