If you’ve been in the frontend industry for a while, then you’ve probably come across or used MobX at least once. If not, then today is your lucky day because this article will tell you why MobX remains a relevant force in the frontend world. We’ll look into its core concepts, explore its strengths and weaknesses, and compare it to other state management solutions.

👁 Mobx Adoption Guide: Overview, Examples, And Alternatives

Without further ado, let’s dive in!

What is MobX?

MobX is a lightweight, boilerplate-free state management library that offers a reactive rather than a functional approach to state management. It helps you track and manage your app’s data without a lot of extra code. When that data changes, MobX automatically updates the parts of your app that need it.

The MobX team developed this solution to address the growing complexity of state management in React applications. While solutions like Redux are more popular, they often require significant boilerplate code, have a steep learning curve, and result in spaghetti code.

MobX provides a more intuitive and less verbose approach to managing state by reducing the amount of boilerplate code and introducing reactive data and automatic updates. It basically makes it impossible to produce an inconsistent state.

At its core, MobX operates on the principle of reactive programming. It uses three main concepts:

• Observables — Represent the state
• Actions — Modify the state
• Reactions — Automatically synchronize the state changes with the UI

This reactive programming model ensures that the UI always reflects the application’s current state without requiring manual synchronization.

MobX uses a virtual dependency tree to track which parts of the state are used by which reactions, ensuring that only the relevant parts of your application update when the state changes.

Further reading:

• Introduction to MobX with React
• A guide to RxJS Observables

Why choose MobX?

Obviously, there are many state management options available in the React ecosystem. So, why use MobX?

The truth is, when it comes to state management, MobX takes a smarter approach and is a breath of fresh air compared to most other solutions. Everyone hates tons of extra code just to keep your app’s data and what users see on screen in sync, and refactoring so much code can be time-consuming and draining.

With MobX, you define your app’s data naturally, and MobX will act like a guard, constantly watching that data. Whenever something changes, MobX automatically updates the parts of your screen that need it. You don’t need to perform manual updates or worry about things being out of sync — MobX keeps everything in perfect harmony.

Plus, MobX is flexible and works with different frameworks, so it fits your development style. And even though it’s easy to use, MobX is a performance powerhouse, keeping your app fast and responsive. In a nutshell, MobX makes state management simple and efficient while letting you focus on building the coolest features for your app.

But like all things, MobX has pros and cons, so let’s examine them now.

Pros of MobX include:

• Ease of use/DX — One of MobX’s greatest strengths is its simplicity. Its straightforward, reactive programming model aligns well with how we naturally think about state management and its changes as developers, reducing the learning curve and encouraging productivity
• Performance — MobX only triggers updates for components that actually need the changed data. This ensures your app remains responsive, even as your state complexity grows
• Relatively small bundle size — Compared to some other state management libraries, MobX boasts a relatively small bundle size, with the core library around 16KB minified and gzipped. As a result, you’ll get faster loading times and a responsive UX, even for large-scale enterprise state management and performance-critical mobile apps
• Community and ecosystem — MobX benefits from a large and active community of developers, so you’ll find plenty of online resources, tutorials, and forums to help you learn and troubleshoot any issues. Additionally, a rich ecosystem of third-party libraries and tools extends MobX’s functionalities, allowing you to tailor your state management solution to specific needs
• Flexible integrations: MobX integrates seamlessly with popular choices like React, Vue, or even plain JavaScript, allowing you to use your existing knowledge and preferences regardless of your chosen framework

Meanwhile, potential drawbacks of using MobX that you should consider include:

• Risk of overusing observables — Since MobX is so easy to use, you might be tempted to make everything observable. However, this might lead to unnecessary reactivity and potential performance issues if not managed carefully
• Potential for scattered state logic — MobX is flexible, but this can lead to state management logic being spread across the application if you’re not careful, potentially making the codebase harder to maintain
• Debugging — Debugging complex MobX applications can be trickier compared to simpler solutions. The asynchronous nature of updates necessitates using your framework’s developer tools extensively to pinpoint issues, which can add time and complexity to the debugging process

In truth, many of MobX’s perceived cons are actually reflections of its core strengths: flexibility, simplicity, and power. While it’s important to consider these factors, MobX’s ability to simplify complex state management, improve code readability, and boost development productivity often outweighs these potential drawbacks.

The key is to evaluate whether MobX’s approach aligns with your project’s needs and your team’s skills.

Further reading:

• Using MobX for large-scale enterprise state management
• Building a full mobile app with TypeScript, Ionic, React, and MobX

Getting started with MobX

To show you MobX in action, let’s create a simple counter application using MobX and compare it to a version using just React Hooks. First, let’s look at a counter using React Hooks:

import { useState } from 'react'; 

function Counter() { const [count, setCount] = useState(0); 

 const increment = () => setCount(count + 1); 
 const decrement = () => setCount(count - 1); 

 return (
 <div> 
 <h1>Count: {count}</h1> 
 <button onClick={increment}>Increment</button> 
 <button onClick={decrement}>Decrement</button> 
 </div> 
 ); 
}

This code defines a simple React functional component called Counter that manages the state of a counter using the useState Hook. To replicate this same functionality with MobX, you have to do this:

import { observable, action } from 'mobx';
import { observer } from 'mobx-react';

const counterStore = observable({
 count: 0,
});

const increment = action(() => {
 counterStore.count++;
});

const decrement = action(() => {
 counterStore.count--;
});

const Counter = observer(() => (
 <div>
 <h1>Count: {counterStore.count}</h1>
 <button onClick={increment}>Increment</button>
 <button onClick={decrement}>Decrement</button>
 </div>
));


export default Counter;

Here, instead of using useState, MobX utilizes an observable state object counterStore, which allows multiple parts of your application to access and react to the state changes.

State updates happen through actions like increment and decrement decorated with action. This helps MobX track changes and efficiently update dependent components.

Finally, the observer decorator on the Counter component ensures it automatically re-renders whenever the counterStore changes.

This approach offers benefits like easier state management across components and automatic UI updates based on state changes.

Key MobX features to know

We briefly defined observers, actions, and reactions above. But there’s much more to MobX that you should know! Let’s take a look at some of the standout features that make MobX so great.

Observers

Observers are components that track and react to changes in the observable state. They help ensure that the UI stays in sync with the underlying state. In React, you can create an observer component using the observer higher-order component or the useObserver Hook:

import { observer } from 'mobx-react';

const Counter = observer(() => (
 <div>
 <h1>Count: {counterStore.count}</h1>
 <button onClick={increment}>Increment</button>
 <button onClick={decrement}>Decrement</button>
 </div>
));

Actions

Actions are functions decorated with @action from MobX, and they represent the authorized ways to modify the MobX state. MobX tracks changes made within actions, ensuring efficient updates and notifying dependent observers:

import { action } from 'mobx';

const increment = action(() => {
 counterStore.count++;
});

const decrement = action(() => {
 counterStore.count--;
});

Derivations/Reactions

Derivations (also called reactions) are pure functions that react to changes in the MobX state and return a derived value. Like everything else in MobX, they are computationally efficient and only re-run when the relevant parts of the state change:

const isEven = reaction(
 () => counterStore.count % 2 === 0,
 (isEven) => {
 console.log("Count is even:", isEven);
 }
);

Stores

Stores are central locations for managing application state. They serve as the single source of truth for the state and encapsulate observables, actions, and other MobX concepts, promoting maintainability.

Selectors

Selectors are functions that derive data from the state. They’re similar to computed values but are used more for component-level computations.

Let’s take an example where you structure your store and component. First, let’s define the store with a selector to filter active items:

import { makeAutoObservable } from 'mobx';

class Store {
 items = [
 { id: 1, name: 'Item 1', isActive: true },
 { id: 2, name: 'Item 2', isActive: false },
 { id: 3, name: 'Item 3', isActive: true },
 ];

 constructor() {
 makeAutoObservable(this);
 }

 get activeItems() {
 return this.items.filter(item => item.isActive);
 }
}

const store = new Store();
export { store };

In this store, items is an observable array representing the items, and activeItems is a computed value (selector) that filters and returns only the active items. Now, let’s use this selector in the ItemList component:

import React from 'react';
import { observer } from 'mobx-react-lite';
import { store } from './store';

const ItemList = observer(() => {
 return (
 <ul>
 {store.activeItems.map(item => (
 <li key={item.id}>{item.name}</li>
 ))}
 </ul>
 );
});

export default ItemList;

Here, ItemList is an observer component that will automatically re-render whenever activeItems in the store changes. The component itself uses the activeItems selector from the store to render the list of active items.

Classes/Inheritance

While MobX supports classes and inheritance, composition with plain objects often proves to be a more efficient and maintainable approach for state management in MobX applications.

Custom Hooks

MobX allows us to create custom Hooks to encapsulate reusable state management logic. This promotes code reusability and well-structured applications.

Use cases for MobX

MobX is well-suited for a variety of applications, particularly those with complex state management needs:

• Medium- to large-scale applications — In complex applications with intricate data flows, MobX simplifies state management and enhances code maintainability
• Real-time applications — MobX’s reactive nature makes it ideal for real-time applications where data updates need to reflect instantaneously across components
• Form-heavy applications — MobX can simplify the management of form state, especially in complex, multi-step forms
• Collaborative applications — Applications with collaborative features benefit from MobX’s automatic updates, ensuring all users see the latest state changes

When NOT to use MobX

While MobX offers numerous advantages, it’s not a one-size-fits-all solution. Here are some situations where you might consider alternatives:

• Small, simple applications — For small applications with minimal state management needs, the overhead of learning MobX might outweigh its benefits
• Legacy codebases — Introducing MobX into a large, established codebase can be challenging. Evaluate the integration effort and potential benefits compared to existing state management solutions
• Team unfamiliarity — If your development team lacks experience with MobX, the learning curve might create a barrier to adoption

Deploying your MobX project

Deploying an application that uses MobX follows the same principles as deploying any other frontend project. However, here are some best practices to keep in mind:

• Tree shaking — Utilize tree shaking offered by modern bundlers (like webpack) to eliminate unused MobX code from your production bundle, resulting in a smaller overall size
• Production mode — Ensure you’re using MobX in production mode, which optimizes performance and removes unnecessary features
• Testing — Implement thorough unit and integration tests to ensure your MobX application behaves as expected in production
• Server-side rendering — Consider server-side rendering for improved initial load performance and SEO

Further reading:

• Tree shaking and code splitting in webpack
• Comparing React testing libraries
• A guide to Vitest automated testing with Vue components
• JavaScript testing: 9 best practices to learn
• SSG vs. SSR in Next.js

MobX vs. similar (Redux, Zustand)

Several other state management libraries compete with MobX in the frontend ecosystem. Let’s compare MobX with two popular alternatives: Redux and Zustand:

	MobX	Redux	Zustand
State management approach	Uses observable state that automatically updates dependent components when it changes	Enforces a unidirectional data flow where actions trigger state updates in a centralized store	Offers minimal state management capabilities. You manually update the state or re-render components depending on changes
Performance	Excellent for complex, frequently updating state due to its fine-grained reactivity system	Good overall, but may require optimizations for large apps. Time-travel debugging can be a performance boon for development	Very good, especially for React apps. Its minimal approach leads to efficient updates and renders
Supported frameworks/libraries	Works seamlessly with React, Vue, Angular, and plain JavaScript	Primarily used with React, but integrations exist for other frameworks	Designed for React, but can be adapted for other frameworks with effort
Community	Large and active	Large, extensive support	Smaller but growing
Documentation/resources	Well-documented with comprehensive guides and API reference	Extensive documentation, tutorials, and third-party resources available	Concise documentation, focusing on essential concepts and API
Ideal use case	Complex applications with interconnected, frequently changing states where a reactive model is beneficial	Large-scale applications requiring strict state management, predictable state changes, and extensive debugging capabilities	Small to medium React applications needing simple state management with minimal setup and boilerplate

This comparison table should help you assess these popular solutions and determine which option might best fit your needs.

Further reading:

• Redux vs. MobX: Which performs better?
• Managing React state with Zustand
• Exploring Zedux and how it compares to Redux
• A guide to choosing the right React state management solution

Conclusion

MobX offers a powerful and flexible approach to state management in frontend applications. Its reactive nature and minimal boilerplate make it an attractive option for developers looking to simplify their state management code while maintaining performance.

While MobX may not be the best fit for every project, its strengths in handling complex, frequently updating state make it an excellent choice for many modern web applications. As with any technology choice, it’s crucial to evaluate MobX against your specific project requirements and team preferences.

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