Contents
  1. What is RxJS?
  2. RxJS License and Free Usage
  3. Benefits and Use Cases of RxJS
  4. Points to Note and Drawbacks
  5. Practical Example: Creating a Countdown Timer that Decreases Every Second Using RxJS
  6. Summary

What is RxJS?

RxJS (Reactive Extensions for JavaScript) is a library that makes asynchronous and event-based programming easier. It handles complex asynchronous processes by creating data streams and applying various operations to them.

RxJS

RxJS License and Free Usage

RxJS is provided under the MIT License and can be used free of charge. This allows it to be freely used, modified, and distributed in both personal and commercial projects.

Benefits and Use Cases of RxJS

  • Simplification of Asynchronous Processing:
    You can easily describe complex timing and event handling.
  • Unified API:
    Promises, callbacks, events, and various other asynchronous patterns can be handled in a unified way.
  • High Expressiveness:
    With a rich set of operators, you can transform, aggregate, and filter data.

Points to Note and Drawbacks

  • Learning Curve:
    RxJS concepts and operators may feel difficult for beginners.
  • Performance:
    Excessive use may impact performance.

Practical Example: Creating a Countdown Timer that Decreases Every Second Using RxJS

HTML Code

<div id="timer">10</div>

CSS Code

<style>
body {
    font-size: 16px;
    text-align: center;
    margin: 0;
}
h1{
    text-align: center;
    font-size: 20px;
    padding: 10px 0 20px 0;
    line-height: 1.8em;
}
#timer {
    font-size: 20px;
    text-align: center;
}
</style>

Importing the RxJS Library

Add a script tag to import the RxJS library in the section of your HTML file. For example, when importing directly from a CDN:

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/7.4.0/rxjs.umd.min.js"></script>

　

Installing in a Project

If you are using a Node.js project, you need to install RxJS. Run the following command in the command line:

npm install rxjs

　
After that, import RxJS in your JavaScript file.

import * as rxjs from 'rxjs';

JavaScript Code

This code implements a countdown timer where the number decreases every second.

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/7.4.0/rxjs.umd.min.js"></script>
<script>
const { interval } = rxjs;
const { take } = rxjs.operators;

const countdown = interval(1000).pipe(take(11));
countdown.subscribe(val => {
    document.getElementById('timer').textContent = 10 - val;
});
</script>

　
In the above example, we are using “Operators”.

What Are Operators?

Operators are functions used in RxJS to manipulate the data streams generated by Observables. By combining these functions, you can perform complex data transformations and conditional processing.

Benefits
  • Flexible Data Transformation:
    You can use various operators to transform data streams into the required format.
  • Improved Code Readability:
    By using clear function chains, you can express the flow of data in an easy-to-understand way.
  • Reusability:
    By creating custom operators, you can easily reuse code.
Use Cases
  • Data Filtering:
    Use the filter operator to extract only data that meets specific conditions.
  • Data Transformation:
    Use map or flatMap to convert input data into another format.
  • Error Handling:
    Use catchError to handle errors and control the flow of data.

　
Operators are a core part of RxJS and greatly enhance the handling of data streams.

Countdown Timer Demo Page Using RxJS (Number Decreases Every Second)

By opening the demo page below, you can see a countdown timer created with RxJS where the number decreases every second.

Countdown Timer Demo Page Using RxJS (Number Decreases Every Second)

Summary

RxJS is a powerful library for supporting asynchronous processing. Although it has a learning curve for beginners, once understood, it allows you to efficiently manage asynchronous operations. It is especially recommended for applications that handle data streams.

　
*If you reuse this content, please do so at your own responsibility.
Do not reuse the Google Analytics tag included in the head tag of the demo page.*

asynchronous RxJS