useActiveElement 
Reactive document.activeElement
Demo 
Usage 
js
import { useActiveElement } from '@vueuse/core'
const activeElement = useActiveElement()
watch(activeElement, (el) => {
  console.log('focus changed to', el)
})Component Usage 
This function also provides a renderless component version via the
@vueuse/componentspackage. Learn more about the usage.
vue
<template>
  <UseActiveElement v-slot="{ element }">
    Active element is {{ element.dataset.id }}
  </UseActiveElement>
</template>Type Declarations 
typescript
export interface UseActiveElementOptions
  extends ConfigurableWindow,
    ConfigurableDocumentOrShadowRoot {
  /**
   * Search active element deeply inside shadow dom
   *
   * @default true
   */
  deep?: boolean
  /**
   * Track active element when it's removed from the DOM
   * Using a MutationObserver under the hood
   * @default false
   */
  triggerOnRemoval?: boolean
}
/**
 * Reactive `document.activeElement`
 *
 * @see https://vueuse.org/useActiveElement
 * @param options
 */
export declare function useActiveElement<T extends HTMLElement>(
  options?: UseActiveElementOptions,
): Ref<T | null | undefined, T | null | undefined>