RxJS Buffer: An Effective Tool for Data Grouping and Filtering

The RxJS buffer operator stands as a potent tool for the organization and refinement of data. It provides the ability to gather emitted values into an array until a specified notifier triggers. This operator finds utility in various scenarios, including implementing caching strategies, optimizing API call frequency, and mitigating noisy data fluctuations.

In this blog post, we will delve into the buffer operator and illustrate its application in addressing common challenges within Angular applications.

Understanding the Buffer Operator:

The buffer operator operates by accumulating emitted values into an array until a designated notifier emits a signal. This notifier can take various forms, such as a timer, a user action, or any event suitable for signaling the collection of data.

Upon the notifier emitting, the buffer operator dispatches an array containing all the accumulated values. Subsequently, the operator resets and recommences the data collection process.

How to Employ the Buffer Operator:

To harness the buffer operator effectively, you must specify two crucial elements:

The number of values to accumulate before emitting an array. The notifier responsible for triggering the data collection process. The buffer operator can be applied in diverse ways, including:

• Implementing a caching mechanism.
• Reducing the frequency of API calls.
• Smoothing out erratic data fluctuations.

Example: Caching Data with the Buffer Operator:

The following example demonstrates the usage of the buffer operator to implement a caching strategy:

import { fromEvent } from 'rxjs';
import { buffer } from 'rxjs/operators';

const cache = new Map<string, any>();

const getCachedData = async (key) => {
  const cachedData = cache.get(key);
  if (!cachedData) {
    // Perform the API call and store the results in the cache.
    const apiResponse = await fetch('https://api.example.com/slow-api-call');
    const data = await apiResponse.json();

    cache.set(key, data);

    // Return the API response.
    return data;
  }

  // Return the cached data.
  return cachedData;
};

// Utilize the buffer operator to cache API call results every 1000 milliseconds.
const cachedData = getCachedData('my-key').pipe(buffer(1000));

// Subscribe to the cached data observable.
cachedData.subscribe((data) => {
  // Utilize the cached data.
});

In this illustration, the buffer operator is employed to gather API call results at 1000-millisecond intervals. Consequently, the API call is executed only once every 1000 milliseconds, regardless of the number of subscriptions to the observable.

Example: Reducing API Calls with the Buffer Operator:

The subsequent example showcases the utilization of the buffer operator to minimize the frequency of API calls:

import { fromEvent } from 'rxjs';
import { buffer } from 'rxjs/operators';

const apiCall = fromEvent(document, 'click');

// Employ the buffer operator to limit API calls to once per second.
const bufferedApiCall = apiCall.pipe(buffer(1000));

// Subscribe to the buffered API call observable.
bufferedApiCall.subscribe(() => {
  // Initiate the API call.
});

In this scenario, the buffer operator is employed to accumulate clicks on the document every 1000 milliseconds. Consequently, an API call is executed only once per second, even if the user clicks multiple times consecutively.

Example: Smoothing Noisy Data with the Buffer Operator:

The subsequent example demonstrates how to utilize the buffer operator to mitigate data noise:

import { fromEvent } from 'rxjs';
import { buffer } from 'rxjs/operators';

const sensorData = fromEvent(sensor, 'change');

// Employ the buffer operator to smooth sensor data.
const smoothedSensorData = sensorData.pipe(buffer(100));

// Subscribe to the smoothed sensor data observable.
smoothedSensorData.subscribe((data) => {
  // Utilize the smoothed sensor data.
});

In this context, the buffer operator is used to accumulate sensor data every 100 milliseconds. Consequently, updates to the smoothed sensor data are emitted only once every 100 milliseconds, even in the presence of rapid data fluctuations.

• Date: 04 Oct 2023