asyncFilter

The asyncFilter() function filters the elements of a generator according to an asynchronous predicate. It returns an asynchronous generator containing only the elements that satisfy the condition.

Interactive example

Syntax

Classic signature with type guard

function asyncFilter<
	GenericElement extends unknown,
	GenericOutput extends GenericElement,
>(
	iterator: Iterable<GenericElement> | AsyncIterable<GenericElement>,
	predicate: (
		item: GenericElement, 
		params: AsyncGeneratorFilterParams
	) => item is GenericOutput
): AsyncGenerator<GenericOutput, unknown, unknown>

Classic signature with boolean

function asyncFilter<
	GenericElement extends unknown,
>(
	iterator: Iterable<GenericElement> | AsyncIterable<GenericElement>,
	predicate: (
		item: GenericElement, 
		params: AsyncGeneratorFilterParams
	) => boolean
): AsyncGenerator<GenericElement, unknown, unknown>

Curried signature

function asyncFilter<
	GenericElement extends unknown,
>(
	predicate: (
		item: GenericElement, 
		params: AsyncGeneratorFilterParams
	) => boolean
): (
	iterator: Iterable<GenericElement> | AsyncIterable<GenericElement>
) => AsyncGenerator<GenericElement, unknown, unknown>

Parameters

• iterator: The generator (synchronous or asynchronous) to filter
• predicate: Asynchronous filtering function that receives:
  • item: The current element
  • params.index: The element index

Return value

An AsyncGenerator containing the filtered elements.

See also

• filter - Synchronous version of asyncFilter
• asyncMap - Transforms with an async function
• asyncReduce - Reduces with an async function

Sources

• MDN Web Docs - Async iterators