calledByNext

The calledByNext() function registers a callback executed when a new run of the same flow replaces a previous asynchronous run that is still active. A common use case is aborting a previous fetch with AbortController.

Interactive example

Syntax

function calledByNext<
	GenericOutput extends unknown
>(
	theFunction: () => GenericOutput
): AsyncGenerator

Parameters

• theFunction: Callback called when a later run of the same flow arrives before the current run finishes.

Return value

An async generator yielding a calledByNext effect. The callback return value is not returned by the flow.

Notes

• Internal state is stored in a WeakMap keyed by the executed flow reference.
• To share this behavior across calls, reuse the same flow created with F.create(...) or the same function returned by F.toFunction(...).
• An inline F.run(async function *() { ... }) creates a new reference on every call, so it does not share the calledByNext() state.
• If the same execution yields calledByNext(...) multiple times, only the first encountered effect is applied by the runner.

See also

• queue - Serializes or limits concurrent runs of the same flow
• throttling - Ignores or defers runs that happen too close together
• exec - Executes a nested flow inside the current flow