Learn React Hooks from Scratch

Learn React Hooks from scratch. Understand useState, useEffect, useRef, useContext, useMemo, useCallback, custom Hooks, and modern React development best practices.

React Hooks Explained: The Foundation of Modern React Development

As React applications become larger and more interactive, developers need efficient ways to manage state, handle side effects, optimize performance, and share logic between components.

Before React Hooks were introduced, these tasks were primarily handled using Class Components. While class components were powerful, they often resulted in complex and difficult-to-maintain code.

To solve these challenges, React introduced Hooks.

Today, Hooks are one of the most important features in React, and almost every modern React application relies on them.

In this guide, you'll learn what React Hooks are, why they were introduced, and how they help developers build cleaner and more maintainable applications.

Prerequisites

Before learning React Hooks, make sure you understand:

• React Components
• React Props
• React State
• JavaScript Functions

These concepts form the foundation of understanding Hooks.

What Are React Hooks?

React Hooks are special functions that allow functional components to use React features such as state, side effects, context, and more.

Hooks make it possible to build powerful React applications without using class components.

Example:

  import { useState } from "react";

function Counter() {

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

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

The useState Hook allows a functional component to store and update data.

Why Were Hooks Introduced?

Before Hooks, developers often used class components.

Example:

  class Counter extends React.Component {

  state = {
    count: 0
  };

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

Class components introduced concepts such as:

• this
• lifecycle methods
• complex logic organization

As applications grew, code became harder to understand and maintain.

Hooks simplified React development by allowing developers to write the same functionality using simpler functional components.

Benefits of React Hooks

Hooks provide several advantages:

• simpler code
• improved readability
• reusable logic
• better maintainability
• reduced boilerplate
• easier testing

These benefits are the reason Hooks have become the standard approach in modern React development.

Rules of Hooks

React Hooks follow a few important rules.

Only Call Hooks at the Top Level

Correct:

  function App() {

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

  return <h1>{count}</h1>;
}
  

Incorrect:

  if (true) {
  useState(0);
}
  

Hooks should never be called inside:

• conditions
• loops
• nested functions

Only Call Hooks Inside React Components

Correct:

  function App() {
  useState(0);
}
  

Incorrect:

  function calculate() {
  useState(0);
}
  

Hooks are designed specifically for React components and custom Hooks.

Common React Hooks

React provides several built-in Hooks.

useState Hook

The useState Hook allows components to store and update data.

Example:

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

Common use cases:

• counters
• forms
• search inputs
• dark mode toggles
• shopping carts

useEffect Hook

The useEffect Hook performs side effects inside components.

Example:

  useEffect(() => {
  console.log("Component Loaded");
}, []);
  

Common use cases:

• API requests
• event listeners
• document title updates
• timers

useRef Hook

The useRef Hook provides access to DOM elements and persistent values.

Example:

  const inputRef =
  useRef(null);
  

Common use cases:

• focusing inputs
• storing mutable values
• interacting with DOM elements

useContext Hook

The useContext Hook allows components to access shared data without passing props through multiple levels.

Example:

  const theme =
  useContext(ThemeContext);
  

Common use cases:

• authentication
• themes
• language settings
• global application data

useMemo Hook

The useMemo Hook optimizes expensive calculations.

Example:

  const total =
  useMemo(() => {
    return calculateTotal();
  }, [items]);
  

Common use cases:

• filtering large datasets
• expensive calculations
• performance optimization

useCallback Hook

The useCallback Hook memoizes functions.

Example:

  const handleClick =
  useCallback(() => {
    console.log("Clicked");
  }, []);
  

Common use cases:

• preventing unnecessary renders
• optimizing child components

Custom Hooks

One of the most powerful features of Hooks is the ability to create custom Hooks.

Example:

  function useCounter() {

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

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

  return {
    count,
    increment
  };
}
  

Usage:

  const {
  count,
  increment
} = useCounter();
  

Custom Hooks allow developers to reuse logic across multiple components.

Real Project Usage

Blog Application

Hooks can manage:

• search functionality
• category filters
• theme switching
• comment forms

E-commerce Website

Hooks can manage:

• shopping carts
• product filters
• user authentication
• wishlist functionality

Dashboard Application

Hooks can manage:

• API data
• charts
• user preferences
• notifications

Behind the Scenes

React Hooks are essentially JavaScript functions.

Example:

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

React internally keeps track of component state and re-renders the component whenever state changes.

This mechanism allows Hooks to provide powerful functionality while maintaining a simple API.

Common Beginner Mistakes

Calling Hooks Inside Conditions

Incorrect:

  if (isLoggedIn) {
  useState(false);
}
  

Hooks must always be called in the same order.

Forgetting Dependency Arrays

Incorrect:

  useEffect(() => {
  fetchData();
});
  

This runs after every render.

Using Hooks Unnecessarily

Not every variable requires a Hook.

Use Hooks only when React needs to track data or behavior.

Ignoring Custom Hooks

Reusable logic should often be extracted into custom Hooks.

React Hooks Interview Questions

1. What are React Hooks?
2. Why were Hooks introduced?
3. What are the rules of Hooks?
4. What is the purpose of useState?
5. What is useEffect used for?
6. What are Custom Hooks?
7. What is the difference between useMemo and useCallback?
8. Why should Hooks only be called at the top level?

React vs Next.js

React Hooks work exactly the same in React and Next.js.

Whether you're building a React application or a Next.js application, Hooks are the primary way to manage state, side effects, and component behavior.

Understanding Hooks is essential before learning advanced React and Next.js concepts.

Common Real-World Use Cases

React Hooks are commonly used for:

• Dark mode toggles
• Form handling
• API requests
• Search functionality
• Shopping carts
• Authentication systems
• Dashboard analytics
• Notification systems

Almost every modern React application uses Hooks extensively.

Production Tip

Professional React developers usually:

• prefer functional components
• use Hooks instead of class components
• create custom Hooks for reusable logic
• optimize performance with useMemo and useCallback
• keep Hook logic organized and maintainable

Well-structured Hook usage makes applications easier to scale.

Why React Hooks Matter

Hooks help developers:

• write cleaner code
• reuse logic efficiently
• manage component behavior
• improve maintainability
• build scalable applications

They are one of the most important features in modern React development.

Conclusion

React Hooks are special functions that bring state management, side effects, context, and many other React features into functional components.

By simplifying component logic and encouraging reusable patterns, Hooks have become the standard approach for building modern React applications.

Mastering Hooks is an essential step toward becoming a professional React and Next.js developer.