React Functional or Class Components: Everything you need to know

Introduction:
What if I told you there was a way to make your React code easier to understand, test, and perform better? As it turns out, functional components are a simple way to accomplish all of these goals and more.

React, the popular JavaScript library for building user interfaces, provides developers with two primary ways to create components: functional components and class components. With the introduction of React Hooks, functional components have gained more prominence, but class components still play a crucial role in many React applications.

In the bustling world of JavaScript frameworks, React reigns supreme. But for newcomers, navigating its component system can feel like traversing a tangled rainforest. Two key players within this jungle are functional components and class components. Choosing between them is a crucial decision, impacting code maintainability, efficiency, and overall development experience.

In this guide, I will teach you everything you need to know, like why, how, and when to use functional components in React..

React’s Component Showdown: Functional vs. Class—Unmasking the Mystery:

The debate between functional and class components in terms of performance has been a hot topic in the React community. Class components have traditionally been the workhorse, handling lifecycle methods with precision. The introduction of functional components and react hooks, however, has resulted in a significant shift in the landscape.

What are Functional Components?

Functional components are JavaScript functions that take in properties (props) and return React elements. Before the advent of React Hooks, functional components were primarily used for simpler, stateless components, known as “stateless functional components.” They were concise, easy to read, and performed well.

Class components are ES6 classes, and Functional Components are functions. The only constraint for a functional component is to accept props as an argument and return valid JSX.

Let’s take a look:

function Hello(props) {
   return <div> Hello {props.name}</div>;
}

In the above example is a functional component.

The absence of state and lifecycle methods distinguishes this type of component from a class component. This is why functional components are also known as stateless components.

Below is the same component written in ES6:

const Hello = ({name}) => <div>Hello {name}</div>

Here’s the same component, but written as a class component:

class Hello extends Component {
      render() {
         return <div>Hello {this.props.name}</div>;
     }
}

So now you know the key differences that make functional components different from class components.

Benefits of Functional Components:

1. Simplicity:

• Functional components are simpler and shorter. They are only concerned with rendering UI based on props and do not handle state.

2. Simpler Testing:

• Because functional components are pure functions, testing is simple. Without having to deal with component state, you can pass props and test the output.

3. Performance:

• Because functional components are lightweight, they perform better in general. They can now handle state and lifecycle features efficiently thanks to the introduction of React Hooks.

4. Compatibility of Hooks:

• Functional components integrate seamlessly with React Hooks, providing a more natural way to manage state and side effects.

Use Cases for Functional Components:

1. Components with no state:

• Ideal for components with no need for internal state management.

2. Presentation Components:

• Suitable for components with a focus on UI rendering but no complex logic.

What are Class Components?

Class components offer a robust set of lifecycle methods, allowing developers to fine-tune the behavior of their components at different stages. From `componentDidMount` for initial setup to `componentWillUnmount` for cleanup, the lifecycle methods provide a structured approach to managing state and side effects.

However, one drawback is that all lifecycle methods contribute to the component’s overall bundle size, potentially impacting performance. In scenarios where only a subset of lifecycle methods is needed, the extra baggage may seem unnecessary.

A class component can keep its internal state and handle lifecycle events, which are methods that are initiated by default at certain points in the component’s lifecycle, such as when the component first appears or when its status or position changes. They can also respond to lifecycle methods like `componentDidMount()`, `componentDidUpdate()`, and others.

In other words, employing lifecycle methods like componentDidMount and componentWillUnmount to handle various phases of a component’s existence. While this might feel familiar for object-oriented programming (OOP) veterans, it involves more boilerplate code and can be trickier to debug for newbies. But fear not, class components still have their place, particularly for complex state management and performance optimizations.

Here is an example of a class component:

class Header extends React.Component {
     constructor(props) {
        super(props);
        this.state = { text: 'Hello world!' };
      }

      render() {
         return <h1>{this.state.text}</h1>;
     }
}

 

The Header class in the above example is a class component that extends React.Base class for components. The render method returns a JSX element, which is an h1 element displaying a user greeting

The constructor method is used to initialize the state, and the super() method is required to call the parent class React’s constructor. The render() method of a component is used to return the JSX code that describes what the component should render.

It should be noted that functional components with hooks can be used to replace some use cases of class components, which is considered best practice.

Why do developers prefer Functional Components over Class Components?

There are numerous reasons why functional components are preferable to class components when developing using ReactJS, but here are five of the most important.

1. Performance: Functional components are more effective than class components because they lack the overhead of extra features like the ability to use the “this” keyword.

2. Conciseness: Because functional components do not require a render method or a return statement, they are more concise than class components.

3. Simplicity: Because functional components are just plain JavaScript functions, they are often easier to understand and read than class components, which require knowledge of class syntax and lifecycle methods.

4. Hooks: React Hooks, introduced in React v16.8, work only with functional components. They allow developers to gain access to state information.

5. Reusability: Because they do not have this constraint, functional components are more reusable, which can cause problems when supporting a component.

Introduction to React Hooks

React Hooks were introduced in React 16.8 to address some of the limitations of class components and make it possible to use state and other React features in functional components. Hooks provide a more consistent way to manage component logic, making functional components as powerful as class components.

Key React Hooks:

1. useState:

• Enables functional components to manage state.

2. useEffect:

• Allows functional components to perform side effects, such as data fetching or subscriptions, similar to lifecycle methods in class components.

3. useContext:

• Simplifies the usage of the context API within functional components.

4. useReducer:

• An alternative to useState for managing more complex state logic.

Advantages of React Hooks:

1. Code Reusability:

• Hooks promote the reuse of stateful logic across components, reducing redundancy.

2. Easier to Understand:

• Hooks simplify the understanding of component logic by separating concerns into smaller, manageable units.

3. Consistent Lifecycle:

• Hooks provide a consistent way to manage component logic, eliminating the need for lifecycle methods in most cases.

4. Gradual Adoption:

• Hooks allow for a gradual transition from class components to functional components in existing codebases.

Choosing Between Functional and Class Components

The decision between functional and class components often depends on the specific requirements of your application. Here are some considerations to help you make an informed choice:

1. State Management:

• Functional Components: Use functional components when managing state with Hooks is sufficient.
• Class Components: Opt for class components when more complex state management is required.

2. Lifecycle Methods:

• Functional Components: Hooks like useEffect can handle most cases where lifecycle methods are needed.
• Class Components: Choose class components when specific lifecycle methods are crucial for your application.

3. Codebase Modernization:

• Functional Components: If you are working on a modern codebase or starting a new project, functional components with Hooks are the preferred choice.
• Class Components: If your project has an existing codebase with class components, consider migrating gradually or as needed.

4. Third-Party Library Compatibility:

• Functional Components: Many modern libraries and tools are designed to work seamlessly with functional components and Hooks.
• Class Components: If you heavily rely on third-party libraries that expect class components, it might be more convenient to stick with class components.

5. Team Familiarity:

• Functional Components: If your team is more familiar with Hooks and functional components, it might lead to more consistent and maintainable code.
• Class Components: If your team has extensive experience with class components, it might make sense to continue using them, especially in legacy projects.

It’s worth noting that, since the introduction of hooks, the distinction between functional and class components has blurred, so you can use whatever method you want in most cases, but functional components are preferred because there are modern and recommended methods.

Conclusion:

While functional components have improved in terms of performance, the choice between functional and class components isn’t always black and white. The performance difference may be negligible in many cases, and other factors such as code readability and maintainability may take precedence.

Internal optimizations in React have also reduced the performance gap between functional and class components as of 2023. Instead of relying solely on general assumptions, developers are encouraged to profile and measure performance in their specific use cases in order to make informed decisions.

We hope that we have adequately covered this subject. If you have any questions about React components, please post them in the question box below, and our support team will get back to you as soon as possible.

 

Thank you for taking the time to read this article. Happy studying!