Function: count()

count<T>(): Operator<T, number>

Defined in: operators/count.ts:13

Creates a stream operator that counts the number of items emitted by the source stream.

This operator consumes all values from the source stream without emitting anything. Once the source stream completes, it emits a single value, which is the total number of items that were in the source stream. It then completes.

Type Parameters

T

T = any

The type of the values in the source stream.

Returns

Operator<T, number>

An Operator instance that can be used in a stream's pipe method.

Examples

From count.spec.ts:12

let subject: ReturnType<typeof createSubject<number>> = createSubject<number>();

let source: Stream<number> = subject;

const minStream = source.pipe(min());
const results: number[] = [];
(async () => {
  for await (const value of eachValueFrom(minStream)) {
    results.push(value);
  }
})();
subject.next(3);
subject.next(1);
subject.next(2);
subject.complete();
await new Promise((resolve) => setTimeout(resolve, 100));
expect(results).toEqual([1]);