whenever

Usage

import { useAsyncState, whenever } from '@vueuse/core'

const { state, isReady } = useAsyncState(
  fetch('https://jsonplaceholder.typicode.com/todos/1').then(t => t.json()),
  {},
)

whenever(isReady, () => console.log(state))

// this
whenever(ready, () => console.log(state))

// is equivalent to:
watch(ready, (isReady) => {
  if (isReady)
    console.log(state)
})

Callback Function

Same as watch, the callback will be called with cb(value, oldValue, onInvalidate).

whenever(height, (current, lastHeight) => {
  if (current > lastHeight)
    console.log(`Increasing height by ${current - lastHeight}`)
})

Computed

Same as watch, you can pass a getter function to calculate on each change.

// this
whenever(
  () => counter.value === 7,
  () => console.log('counter is 7 now!'),
)

Options

Options and defaults are same with watch.

// this
whenever(
  () => counter.value === 7,
  () => console.log('counter is 7 now!'),
  { flush: 'sync' },
)

Type Declarations

type Truthy<T> = T extends false | null | undefined ? never : T
export interface WheneverOptions<
  Immediate = boolean,
> extends WatchOptions<Immediate> {
  /**
   * Only trigger once when the condition is met
   *
   * Override the `once` option in `WatchOptions`
   *
   * @default false
   */
  once?: boolean
}
/**
 * Shorthand for watching value to be truthy
 *
 * @see https://vueuse.org/whenever
 */
export declare function whenever<T>(
  source: WatchSource<T>,
  cb: WatchCallback<Truthy<T>, T | undefined>,
  options?: WheneverOptions<true>,
): WatchHandle
export declare function whenever<T>(
  source: WatchSource<T>,
  cb: WatchCallback<Truthy<T>, T>,
  options?: WheneverOptions<false>,
): WatchHandle