Mastering React: Building Interactive Components with Modern Hooks

React has revolutionized how we build user interfaces, and with the introduction of hooks, creating stateful components has never been more elegant. In this comprehensive guide, we'll explore how to build interactive, production-ready components using modern React patterns.

Understanding React Hooks

React Hooks were introduced in React 16.8, fundamentally changing how we write components. They allow you to use state and other React features without writing a class component.

The Power of useState

The useState hook is your gateway to adding state to functional components. Here's a simple example:

useState-example.js

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import { useState } from "react";
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function SimpleCounter() {
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  const [count, setCount] = useState(0);
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  return (
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    <div>
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      <p>Count: {count}</p>
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      <button onClick={() => setCount(count + 1)}>Increment</button>
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    </div>
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  );
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}

Key takeaways:

useState returns an array with two elements: the current state and a function to update it
The argument passed to useState is the initial state value
State updates trigger re-renders of your component

useEffect: Managing Side Effects

The useEffect hook lets you perform side effects in function components. It's the combination of componentDidMount, componentDidUpdate, and componentWillUnmount from class components.

useEffect-example.ts {7-15}

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import { useState, useEffect } from "react";
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function DataFetcher() {
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  const [data, setData] = useState(null);
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  const [loading, setLoading] = useState(true);
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  useEffect(() => {
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    async function fetchData() {
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      const response = await fetch("https://api.example.com/data");
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      const result = await response.json();
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      setData(result);
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      setLoading(false);
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    }
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    fetchData();
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  }, []); // Empty dependency array = run once on mount
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  if (loading) return <div>Loading...</div>;
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  return <div>{JSON.stringify(data)}</div>;
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}

Building an Interactive Counter

Let's build a feature-rich counter component that demonstrates multiple hooks working together. This example combines useState and useEffect to create an auto-incrementing counter with pause/resume functionality.

import React, { useState, useEffect } from 'react';
import './styles.css';

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

  useEffect(() => {
    let interval = null;

    if (isActive) {
      interval = setInterval(() => {
        setCount(count => count + 1);
      }, 1000);
    } else if (!isActive && count !== 0) {
      clearInterval(interval);
    }

    return () => clearInterval(interval);
  }, [isActive, count]);

  const handleReset = () => {
    setCount(0);
    setIsActive(false);
  };

  return (
    <div className="counter-container">
      <h1 className="title">React Hooks Counter</h1>
      <div className="counter-display">
        {count}
      </div>
      <div className="button-group">
        <button
          className="btn btn-primary"
          onClick={() => setIsActive(!isActive)}
        >
          {isActive ? '⏸ Pause' : '▶ Start'}
        </button>
        <button
          className="btn btn-secondary"
          onClick={handleReset}
        >
          🔄 Reset
        </button>
        <button
          className="btn btn-success"
          onClick={() => setCount(count + 1)}
        >
          ➕ Add
        </button>
        <button
          className="btn btn-danger"
          onClick={() => setCount(count - 1)}
          disabled={count === 0}
        >
          ➖ Subtract
        </button>
      </div>
      <div className="info">
        <p>Status: <strong>{isActive ? 'Running' : 'Stopped'}</strong></p>
      </div>
    </div>
  );
}

export default function App() {
  return (
    <div className="app">
      <Counter />
    </div>
  );
}

Breaking Down the Code

The counter component above showcases several important concepts:

Multiple State Variables: We use two separate useState calls for count and isActive
Effect Cleanup: The useEffect hook properly cleans up the interval to prevent memory leaks
Conditional Effects: The effect only runs when dependencies change
Event Handlers: Multiple button handlers demonstrate different state updates

counter-logic.js {4-5,7-17}

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function Counter() {
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  // Multiple state hooks
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  const [count, setCount] = useState(0);
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  const [isActive, setIsActive] = useState(false);
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  // Effect with cleanup
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  useEffect(() => {
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    let interval = null;
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    if (isActive) {
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      interval = setInterval(() => {
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        setCount((count) => count + 1);
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      }, 1000);
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    }
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    return () => clearInterval(interval);
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  }, [isActive, count]);
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  // ... rest of component
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}

Best Practices for React Hooks

1. Always Use Dependency Arrays Correctly

One of the most common mistakes is forgetting to include all dependencies in the useEffect dependency array:

dependency-array.js

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// ❌ Bad: Missing dependency
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useEffect(() => {
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  console.log(someValue);
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}, []);
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// ✅ Good: All dependencies included
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useEffect(() => {
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  console.log(someValue);
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}, [someValue]);

2. Use Functional Updates for State

When your new state depends on the previous state, always use the functional form of the state setter:

functional-updates.js

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// ❌ Bad: Direct state reference
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setCount(count + 1);
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// ✅ Good: Functional update
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setCount((prevCount) => prevCount + 1);

This is especially important in useEffect hooks and when dealing with asynchronous operations.

3. Extract Custom Hooks

When you find yourself repeating hook logic, extract it into a custom hook:

custom-hook.ts

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function useCounter(initialValue = 0) {
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  const [count, setCount] = useState(initialValue);
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  const increment = () => setCount((c) => c + 1);
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  const decrement = () => setCount((c) => c - 1);
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  const reset = () => setCount(initialValue);
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  return { count, increment, decrement, reset };
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}
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// Usage
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function MyComponent() {
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  const { count, increment, decrement, reset } = useCounter(0);
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  // ...
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}

Performance Optimization

useMemo and useCallback

For expensive computations or to prevent unnecessary re-renders, use useMemo and useCallback:

optimization.js

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import { useMemo, useCallback } from "react";
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function ExpensiveComponent({ data, onUpdate }) {
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  // Memoize expensive calculation
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  const processedData = useMemo(() => {
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    return data.map((item) => {
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      // Expensive operation
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      return complexCalculation(item);
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    });
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  }, [data]);
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  // Memoize callback
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  const handleClick = useCallback(() => {
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    onUpdate(processedData);
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  }, [processedData, onUpdate]);
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  return <div onClick={handleClick}>{processedData.length} items</div>;
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}

Advanced Patterns

Compound Components Pattern

Create flexible, composable components that work together:

compound-pattern.tsx

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interface TabsContextType {
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  activeTab: string;
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  setActiveTab: (tab: string) => void;
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}
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const TabsContext = createContext<TabsContextType | null>(null);
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function Tabs({ children, defaultTab }) {
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  const [activeTab, setActiveTab] = useState(defaultTab);
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  return (
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    <TabsContext.Provider value={{ activeTab, setActiveTab }}>
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      <div className="tabs">{children}</div>
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    </TabsContext.Provider>
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  );
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}
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function TabList({ children }) {
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  return <div className="tab-list">{children}</div>;
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}
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function Tab({ id, children }) {
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  const context = useContext(TabsContext);
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  return (
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    <button
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      className={context.activeTab === id ? "active" : ""}
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      onClick={() => context.setActiveTab(id)}
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    >
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      {children}
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    </button>
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  );
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}
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// Usage
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<Tabs defaultTab="home">
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  <TabList>
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    <Tab id="home">Home</Tab>
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    <Tab id="profile">Profile</Tab>
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  </TabList>
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</Tabs>;

Real-World Application

Let's look at how these patterns come together in a real application. Consider a form with validation:

form-validation.js

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function RegistrationForm() {
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  const [formData, setFormData] = useState({
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    email: "",
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    password: "",
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    confirmPassword: "",
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  });
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  const [errors, setErrors] = useState({});
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  const [touched, setTouched] = useState({});
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  useEffect(() => {
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    // Validate on change
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    const newErrors = {};
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    if (touched.email && !formData.email.includes("@")) {
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      newErrors.email = "Invalid email";
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    }
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    if (touched.password && formData.password.length < 8) {
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      newErrors.password = "Password must be 8+ characters";
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    }
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    if (
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      touched.confirmPassword &&
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      formData.password !== formData.confirmPassword
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    ) {
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      newErrors.confirmPassword = "Passwords do not match";
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    }
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    setErrors(newErrors);
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  }, [formData, touched]);
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  const handleChange = (field) => (e) => {
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    setFormData((prev) => ({
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      ...prev,
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      [field]: e.target.value,
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    }));
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  };
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  const handleBlur = (field) => () => {
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    setTouched((prev) => ({
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      ...prev,
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      [field]: true,
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    }));
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  };
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  return (
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    <form>
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      <input
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        type="email"
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        value={formData.email}
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        onChange={handleChange("email")}
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        onBlur={handleBlur("email")}
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      />
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      {errors.email && <span>{errors.email}</span>}
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      {/* More fields... */}
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    </form>
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  );
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}

Testing React Hooks

Testing components with hooks requires special consideration:

counter.test.js

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import { render, screen, fireEvent, act } from "@testing-library/react";
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import Counter from "./Counter";
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describe("Counter Component", () => {
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  test("increments counter on button click", () => {
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    render(<Counter />);
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    const button = screen.getByText("Increment");
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    const display = screen.getByText(/count:/i);
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    expect(display).toHaveTextContent("Count: 0");
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    fireEvent.click(button);
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    expect(display).toHaveTextContent("Count: 1");
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  });
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  test("auto-increment works correctly", async () => {
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    jest.useFakeTimers();
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    render(<Counter />);
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    const startButton = screen.getByText("Start");
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    fireEvent.click(startButton);
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    act(() => {
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      jest.advanceTimersByTime(3000);
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    });
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    expect(screen.getByText(/count:/i)).toHaveTextContent("Count: 3");
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    jest.useRealTimers();
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  });
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});

Common Pitfalls to Avoid

1. Stale Closures

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// ❌ Problem: Stale closure
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useEffect(() => {
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  const interval = setInterval(() => {
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    setCount(count + 1); // count is stale
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  }, 1000);
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  return () => clearInterval(interval);
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}, []); // Empty deps
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// ✅ Solution: Use functional update
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useEffect(() => {
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  const interval = setInterval(() => {
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    setCount((c) => c + 1); // Always fresh
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  }, 1000);
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  return () => clearInterval(interval);
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}, []);

2. Infinite Loops

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// ❌ Infinite loop
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useEffect(() => {
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  setData(newData);
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}, [data]); // Re-runs every time data changes
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// ✅ Conditional update
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useEffect(() => {
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  if (shouldUpdate) {
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    setData(newData);
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  }
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}, [shouldUpdate]);

3. Missing Cleanup

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// ❌ Memory leak
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useEffect(() => {
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  const subscription = subscribe(callback);
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}, []);
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// ✅ Proper cleanup
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useEffect(() => {
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  const subscription = subscribe(callback);
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  return () => subscription.unsubscribe();
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}, [callback]);

Conclusion

React hooks have fundamentally changed how we write React applications. They provide:

Simpler code: No more class components and binding
Better reusability: Custom hooks make logic portable
Improved performance: Fine-grained control over re-renders
Enhanced developer experience: More intuitive and easier to test

The key to mastering hooks is understanding:

How closures work in JavaScript
The component lifecycle
Dependency arrays and when effects run
When to optimize and when not to

Keep practicing with real-world examples, and you'll find hooks becoming second nature. The interactive examples in this article demonstrate how these concepts come together to create beautiful, functional user interfaces.

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