Vize
whenever
Run a callback whenever a source becomes (or changes while) truthy.
| Package | @vizejs/composable/whenever |
| Own the source | vize lib pull composable:whenever |
| Runtime exports | whenever |
| Gzip budget | 1024 B |
Usage
import { whenever } from "@vizejs/composable/whenever";
Runtime contract
| Utility | Category | Stability | SSR | Hydration | Cleanup | Targets | Host globals | Uses |
|---|---|---|---|---|---|---|---|---|
whenever |
reactivity | experimental | safe | not-applicable | caller, reactive-scope | web, server, worker, native, desktop, terminal | — | — |
API
whenever
Run a callback whenever a source becomes (or changes while) truthy. The callback's value is narrowed with Exclude<Value, Falsy>, so a Ref<User | null> delivers User. With once, the watcher stops after the first truthy delivery, not after the first change (unlike Vue's once). With immediate, an already-truthy source is delivered right away. Safe during server rendering and bound to the owning scope.
function whenever<Value>( source: WatchSource<Value>, callback: ( value: Exclude<Value, Falsy>, oldValue: Value | undefined, onCleanup: WatchCleanupRegistrar, ) => void, options: WheneverOptions = {}, ): WatchHandle
whenever(currentUser, (user) => greet(user.name), { immediate: true, once: true });