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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.:

js

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

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

js

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