ShadowRoot.delegatesFocus

The delegatesFocus read-only property of the ShadowRoot interface returns a boolean that indicates whether delegatesFocus was set when the shadow was attached (see Element.attachShadow()).

var df = shadowRoot.delegatesFocus

A boolean value — true if the shadow root does delegate focus, false if it doesn't.

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

  ...

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