useEffectOnce

Run one browser-client effect with optional unmount cleanup.

What it does

useEffectOnce is a convenience wrapper around useEffect with an empty key list. It runs on the first browser-client build and preserves its cleanup until the hook is removed.

Signature and parameters

void useEffectOnce(Dispose? Function() effect)

effect runs synchronously and may return a synchronous Dispose callback. The hook returns nothing.

Usage

useEffectOnce(() {
  analytics.openPage();
  return analytics.closePage;
});

Live demo

Interactive useEffectOnce demo

Effect-once runs 0 • rebuilds 0

Ownership and lifecycle

The hook owns the returned cleanup and invokes it at client unmount. The callback instance from the initial run remains captured; later builds do not replace the effect.

Server rendering

The effect and cleanup are skipped during server and static rendering. They start independently when the browser hook tree builds.

Common mistakes

Do not use this hook merely to avoid thinking about dependencies. If the operation depends on changing values, use keyed useEffect. Never return a Future; return synchronous cleanup and launch asynchronous work separately.

useMount omits cleanup, useUnmount runs only cleanup, and useUpdateEffect skips the first client build.