ShadowRoot: delegatesFocus property

The delegatesFocus read-only property of the ShadowRoot interface returns true if the shadow root delegates focus, and false otherwise.

If true, when a non-focusable part of the shadow DOM is clicked, or .focus() is called on the host element, the first focusable part inside the host's shadow DOM is given focus, and the shadow host is given any available :focus styling.

Focus is of particular importance for keyboard users (including those using screen readers). delegatesFocus default behavior is to focus the first focusable element — which may be undesirable if that element is not meant to be part of the tabbing order (for example, an element with tabindex="-1"), or if a more 'important' focusable element should receive initial focus (for instance, the first text field rather than the 'close' button which precedes it). In such cases, the autofocus attribute can be specified on the element which should receive initial focus. Use the autofocus attribute with caution as it can introduce accessibility issues, such as bypassing important content which may go unnoticed due to focus being set to an element later in the DOM order.

The property value is originally set using the delegatesFocus property of the object passed to Element.attachShadow(), or using the shadowrootdelegatesfocus attribute of the <template> element when a shadow root is created declaratively.

let customElem = document.querySelector("my-shadow-dom-element");
let shadow = customElem.shadowRoot;

// ...

// Does it delegate focus?
let hostElem = shadow.delegatesFocus;