filter

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

Interactive example

Syntax

Classic signature with type guard

function filter<
	GenericElement extends unknown,
	GenericOutput extends GenericElement,
>(
	iterator: Iterable<GenericElement>,
	predicate: (item: GenericElement, params: GeneratorFilterParams) => item is GenericOutput
): Generator<GenericOutput, unknown, unknown>

Classic signature with boolean

function filter<
	GenericElement extends unknown,
>(
	iterator: Iterable<GenericElement>,
	predicate: (item: GenericElement, params: GeneratorFilterParams) => boolean
): Generator<GenericElement, unknown, unknown>

Curried signature

function filter<
	GenericElement extends unknown,
>(
	predicate: (item: GenericElement, params: GeneratorFilterParams) => boolean
): (iterator: Iterable<GenericElement>) => Generator<GenericElement, unknown, unknown>

Parameters

• iterator: The generator to filter
• predicate: Filtering function that receives:
  • item: The current element
  • params.index: The element index

Return value

A new Generator containing the filtered elements.

See also

• asyncFilter - Asynchronous version of filter
• map - Transforms the elements of a generator
• reduce - Reduces a generator to a value

Sources

• MDN Web Docs - Array.prototype.filter()