Element: shadowRoot property

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 Element.shadowRoot read-only property represents the shadow root hosted by the element.

Use Element.attachShadow() to add a shadow root to an existing element.

Value

A ShadowRoot object instance, or null if the associated shadow root was attached with its mode set to closed. (See Element.attachShadow() for further details).

Some built-in elements, such as and , have user-agent shadow roots that are closed to script. Therefore, their shadowRoot property is always null.

Examples

The following snippets are taken from our life-cycle-callbacks example (see it live also), which creates an element that displays a square of a size and color specified in the element's attributes.

Inside the element's class definition we include some life cycle callbacks that make a call to an external function, updateStyle(), which actually applies the size and color to the element. You'll see that we are passing it this (the custom element itself) as a parameter.

js
class Square extends HTMLElement {
  connectedCallback() {
    console.log("Custom square element added to page.");
    updateStyle(this);
  }

  attributeChangedCallback(name, oldValue, newValue) {
    console.log("Custom square element attributes changed.");
    updateStyle(this);
  }
}

In the updateStyle() function itself, we get a reference to the shadow DOM using Element.shadowRoot. From here we use standard DOM traversal techniques to find the