useMounted 
Mounted state in ref.
Demo 
mounted
Usage 
ts
import { useMounted } from '@vueuse/core'
const isMounted = useMounted()Which is essentially a shorthand of:
ts
const isMounted = ref(false)
onMounted(() => {
  isMounted.value = true
})Type Declarations 
ts
/**
 * Mounted state in ref.
 *
 * @see https://vueuse.org/useMounted
 *
 * @__NO_SIDE_EFFECTS__
 */
export declare function useMounted(): ShallowRef<boolean, boolean>