React Components Explained: Function vs Class Components

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React in JavaScript has remained quite popular as a library for building user interfaces. In React components, developers primarily find two types: Class components and Function components. A person working with React is obliged to know the differences between these two basic categories. The following article makes an attempt to show the most important distinctions together with the benefits and use cases of Function and Class Components.

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Introduction to React Components

React components represent the core of any React application. Using these components, developers can break down complex user interface elements into smaller, reusable parts. Components can be written by using functions or classes. Each of them explains a characteristic benefit for writing components.

Function Components

Function components are clear JavaScript functions that return JSX. It is the simplest way to define a component in the React.

import React from 'react';

function Greeting(props) {
    return <h1>Hello, {props.name}!</h1>;
}

export default Greeting;

Advantages:

Simplicity: Function components are simpler to read and write because of their smooth syntax.
Performance: In general, they are superior in performance because they are simpler and have no additional overhead that class components have.
Hooks: Since React 16.8, using React Hooks, function components can hold state and manage side effects, which in the past were only possible in class components.

Class Components

Class components are ES6 classes that extend from React.Component. They must contain a render() method that returns JSX.

import React, { Component } from 'react';

class Greeting extends Component {
    render() {
        return <h1>Hello, {this.props.name}!</h1>;
    }
}

export default Greeting;

Advantages

State Management: Prior to hooks, class components were the only way to manage local component state.
Lifecycle Methods: Class components have more fine-grained control over component lifecycle events like mounting, updating and unmounting.

Comparing Function and Class Components

Performance
Function components are generally faster and more efficient because there are plain JavaScript functions without the additional complexity that classes have. But most times, the difference in performance is negligible for most applications.

State and Lifecycle
Earlier, the one criterion that function components couldn't fulfill was state handling and lifecycle methods. Now, as of React 16.8, Hooks came into being, and function component can now take charge of state and lifecycle events.

Hooks
Hooks are functions provided by React in order to make state and other capabilities available to function components. Hooks, such as useState, make possible effective state management, while others provide possibilities to work with side effects, for example.

import React, { useState, useEffect } from 'react';

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

    useEffect(() => {
        document.title = `Count: ${count}`;
    }, [count]);

    return (
        <div>
            <p>{count}</p>
            <button onClick={() => setCount(count + 1)}>Increment</button>
        </div>
    );
}

export default Counter;

When to Use Each

Function Components: Use function components for simpler components that don't need lifecycle methods, or for components that rely on hooks for state management and side effects.
Class Components: When working with a legacy codebase or a library that requires a class component, or when you need to use certain lifecycle methods because they are complicated and not easily handled by hooks.

Conclusion

Both function and class components have been the building blocks of React development. The introduction of Hooks brought many new features into function components, making them powerful and performant in most cases. Knowing both kinds of components, their purposes, and their relative strengths allows developers to make an informed decision when building React applications.

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Top comments (3)

Rense Bakker • Jun 13

No. Class components are deprecated as per the React docs. Forget what you know about lifecycle methods and use hooks instead. Lifecycle methods were an abomination that made people do horrible things to the www.