audit

Ignores source values for duration milliseconds, then emits the most recent value from the source Observable, then repeats this process.

Unlike throttle which emits the first value, audit emits the last value.

Completing it, or its source completing, passes on the value its timer is still holding before the completion; dispose() drops that value.

Marble Diagram

audit(250)

Example

//  Timeline (250ms audit):
//
//  Time(x50ms)  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0
//
//  input$       0       2   3                   9   10  11  12  13  14
//               |- 250ms -> |- 250ms ->         |- 250ms -> |- 250ms ->
//  audited$               2           3                   11          14   (emitted at end of window)
//
//  Explanation:
//  - audit emits the LAST value received during each time window
//  - Unlike throttle (which emits the FIRST value), audit emits the LAST
//  - Useful when you want the most recent value after a burst of events

const input$ = source<number>();

const audited$ = input$.pipe(audit(250));

const valueHistory: number[] = [];

audited$.subscribe((value) => {
    valueHistory.push(value);
});

const sleep = (ms: number): Promise<void> =>
    new Promise((resolve) => {
        setTimeout(resolve, ms);
    });

input$.next(0);

await sleep(200);

input$.next(2);

assert.deepStrictEqual(valueHistory, []);

await sleep(100);

assert.deepStrictEqual(valueHistory, [2]);

input$.next(3);

await sleep(300);

assert.deepStrictEqual(valueHistory, [2, 3]);

await sleep(300);

input$.next(9);

await sleep(100);

input$.next(10);

await sleep(100);

input$.next(11);

assert.deepStrictEqual(valueHistory, [2, 3]);

await sleep(100);

assert.deepStrictEqual(valueHistory, [2, 3, 11]);

input$.next(12);

await sleep(100);

input$.next(13);

assert.deepStrictEqual(valueHistory, [2, 3, 11]);

await sleep(100);

input$.next(14);

assert.deepStrictEqual(valueHistory, [2, 3, 11]);

await sleep(100);

assert.deepStrictEqual(valueHistory, [2, 3, 11, 14]);

View source on GitHub