buffertime.md

bufferTime

signature: bufferTime(bufferTimeSpan: number, bufferCreationInterval: number, scheduler: Scheduler): Observable

Collect emitted values until provided time has passed, emit as array.

Why use bufferTime?

The key distinction between bufferTime and other buffering operators lies in its time-based buffering approach. bufferTime accumulates values from the source observable in an array over a specified time duration before emitting the buffered array.

This operator is particularly well-suited for scenarios where you need to batch or throttle emissions from high-frequency observables, such as monitoring user interactions, tracking mouse movements, or dealing with rapidly updating data streams. bufferTime provides an efficient way to handle and process these emissions in a more manageable, time-based manner.

Remember, bufferTime allows you to manage data emissions effectively by collecting and emitting them in time-based batches, as illustrated in the first example. Be mindful of its implications, though, and choose the right operator according to your specific use case.

Examples

Example 1: Buffer for 2 seconds

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { interval } from 'rxjs';
import { bufferTime } from 'rxjs/operators';

//Create an observable that emits a value every 500ms
const source = interval(500);
//After 2 seconds have passed, emit buffered values as an array
const example = source.pipe(bufferTime(2000));
//Print values to console
//ex. output [0,1,2]...[3,4,5,6]
const subscribe = example.subscribe(val =>
  console.log('Buffered with Time:', val)
);

Example 2: Multiple active buffers

( StackBlitz | jsBin | jsFiddle )

// RxJS v6+
import { interval } from 'rxjs';
import { bufferTime } from 'rxjs/operators';

//Create an observable that emits a value every 500ms
const source = interval(500);
/*
bufferTime also takes second argument, when to start the next buffer (time in ms)
for instance, if we have a bufferTime of 2 seconds but second argument (bufferCreationInterval) of 1 second:
ex. output: [0,1,2]...[1,2,3,4,5]...[3,4,5,6,7]
*/
const example = source.pipe(bufferTime(2000, 1000));
//Print values to console
const subscribe = example.subscribe(val =>
  console.log('Start Buffer Every 1s:', val)
);

Additional Resources

• bufferTime 📰 - Official docs
• bufferTime - In Depth Dev Reference
• Time based operators comparison

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📁 Source Code: https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/bufferTime.ts