search
HomeWeb Front-endJS TutorialReusable, Extensible and Testable State Logic with Reactive Programming.

Reusable, Extensible and Testable State Logic with Reactive Programming.

State in UI Components

When we start introducing state into a UI component it is often tempting to do something like this:

Simple Counter Example in Svelte:

<script>
  let count = $state(0);
</script>

<button onclick="{()"> count++}>
  clicks: {count}
</button>

Problem

We use Svelte here but same the issue can apply in any UI framework.

Off the bat we have tightly coupled our state logic with the component - the increment functionality is coded right in the template.

With this set up we can not reuse the counter logic in:

  • other UI components
  • other business logic that requires a counter
  • other UI frameworks

We also cannot test the counter logic without rendering the component. If the component has other functionality coupled with it, isolating the counter logic would not be possible.

Solution:

Separate state logic from the UI component so it can be implemented and tested independently. This will make the logic more reusable and UI components only need to listen for state changes and render. Consider the following:

<script>
  import { RxCounter } from './RxCounter';

  const [count, { increment }] = RxCounter();
</script>

<button onclick="{increment}">
  Count: {$count}
</button>

See full example on StackBlitz

If you compare above with our original example, all the logic for the counter is now encapsulated in RxCounter (we will show the implementation later).

count is an RxJS Observable that emits the new count state. increment is an action method the UI can call to invoke state changes.

Svelte has a nice built in way of subscribing to observables in the template as seen with the $count template variable. Subscribing to an observable in any UI framework is not terribly difficult, and many frameworks have APIs to help accomplish this.

Implementing RxCounter

Information and Disclaimer: We will make use of Reactables API created by the author. It is a state management solution that leverages RxJS to make reactive programming easier.

Get the Reactables Core Package and create RxCounter.

npm i @reactables/core

import { RxBuilder } from '@reactables/core';

export const RxCounter = () =>
  RxBuilder({
    initialState: 0,
    reducers: {
      increment: (count) => count + 1,
    },
  });

RxBuilder returns a Reactable.

A Reactable is a tuple with its first item being an RxJS Observable emitting state changes and second item being a dictionary of action methods for triggering state updates.

The state is reactive, meaning the state responds to changes via its reducer functions. When an increment action triggered by the UI is received, the reactable reacts and its observable emits the new state.

Note RxCounter is now completely decoupled from the view layer and can be used in any UI framework!

Testing the Counter

To test a Reactable, we subscribe to its state observable and invoke its action methods to test its behaviour. We can assert the observable's emitted values matches the desired behaviour.

This can be done with RxJS’s built in Marble Testing.

<script>
  let count = $state(0);
</script>

<button onclick="{()"> count++}>
  clicks: {count}
</button>

Extending the Counter

With the state logic isolated from the view, we can also extend the functionality of RxCounter and create a RxDoubleCounter that has the ability to double the count.

<script>
  import { RxCounter } from './RxCounter';

  const [count, { increment }] = RxCounter();
</script>

<button onclick="{increment}">
  Count: {$count}
</button>

See full example on StackBlitz

Conclusion

Implementing state logic directly in UI components makes the logic harder to reuse and test.

We can program the state logic reactively with Reactables and test it in isolation. This produces a unit of reactive state logic that is highly reusable in both the view and logic layer.

We did a simple counter example here, but Reactables are extensible and composable for much more complex state management scenarios (i.e data fetching, forms etc...). Check out the docs to learn more!

The above is the detailed content of Reusable, Extensible and Testable State Logic with Reactive Programming.. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
JavaScript in Action: Real-World Examples and ProjectsJavaScript in Action: Real-World Examples and ProjectsApr 19, 2025 am 12:13 AM

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.

JavaScript and the Web: Core Functionality and Use CasesJavaScript and the Web: Core Functionality and Use CasesApr 18, 2025 am 12:19 AM

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.

Understanding the JavaScript Engine: Implementation DetailsUnderstanding the JavaScript Engine: Implementation DetailsApr 17, 2025 am 12:05 AM

Understanding how JavaScript engine works internally is important to developers because it helps write more efficient code and understand performance bottlenecks and optimization strategies. 1) The engine's workflow includes three stages: parsing, compiling and execution; 2) During the execution process, the engine will perform dynamic optimization, such as inline cache and hidden classes; 3) Best practices include avoiding global variables, optimizing loops, using const and lets, and avoiding excessive use of closures.

Python vs. JavaScript: The Learning Curve and Ease of UsePython vs. JavaScript: The Learning Curve and Ease of UseApr 16, 2025 am 12:12 AM

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Python vs. JavaScript: Community, Libraries, and ResourcesPython vs. JavaScript: Community, Libraries, and ResourcesApr 15, 2025 am 12:16 AM

Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

From C/C   to JavaScript: How It All WorksFrom C/C to JavaScript: How It All WorksApr 14, 2025 am 12:05 AM

The shift from C/C to JavaScript requires adapting to dynamic typing, garbage collection and asynchronous programming. 1) C/C is a statically typed language that requires manual memory management, while JavaScript is dynamically typed and garbage collection is automatically processed. 2) C/C needs to be compiled into machine code, while JavaScript is an interpreted language. 3) JavaScript introduces concepts such as closures, prototype chains and Promise, which enhances flexibility and asynchronous programming capabilities.

JavaScript Engines: Comparing ImplementationsJavaScript Engines: Comparing ImplementationsApr 13, 2025 am 12:05 AM

Different JavaScript engines have different effects when parsing and executing JavaScript code, because the implementation principles and optimization strategies of each engine differ. 1. Lexical analysis: convert source code into lexical unit. 2. Grammar analysis: Generate an abstract syntax tree. 3. Optimization and compilation: Generate machine code through the JIT compiler. 4. Execute: Run the machine code. V8 engine optimizes through instant compilation and hidden class, SpiderMonkey uses a type inference system, resulting in different performance performance on the same code.

Beyond the Browser: JavaScript in the Real WorldBeyond the Browser: JavaScript in the Real WorldApr 12, 2025 am 12:06 AM

JavaScript's applications in the real world include server-side programming, mobile application development and Internet of Things control: 1. Server-side programming is realized through Node.js, suitable for high concurrent request processing. 2. Mobile application development is carried out through ReactNative and supports cross-platform deployment. 3. Used for IoT device control through Johnny-Five library, suitable for hardware interaction.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

PhpStorm Mac version

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool

Atom editor mac version download

Atom editor mac version download

The most popular open source editor