useWindowFocus 
Reactively track window focus with window.onfocus and window.onblur events.
Demo 
💡 Click somewhere outside of the document to unfocus.
Usage 
js
import { useWindowFocus } from '@vueuse/core'
const focused = useWindowFocus()Component Usage 
This function also provides a renderless component version via the
@vueuse/componentspackage. Learn more about the usage.
vue
<template>
  <UseWindowFocus v-slot="{ focused }">
    Document Focus: {{ focused }}
  </UseWindowFocus>
</template>Type Declarations 
typescript
/**
 * Reactively track window focus with `window.onfocus` and `window.onblur`.
 *
 * @see https://vueuse.org/useWindowFocus
 */
export declare function useWindowFocus(
  options?: ConfigurableWindow,
): Ref<boolean>