In this tutorial, you will learn how to create your own custom React hooks from scratch. React hooks are a powerful feature that allows you to reuse stateful logic across multiple components. We will start by exploring the basics of hooks and their benefits, before diving into the step-by-step process of creating a custom hook. By the end of this tutorial, you will have a solid understanding of how to create your own custom hooks and how they can help you build more efficient and reusable React applications.

What are the React Hooks? 🪝

React hooks are a way to write reusable and stateful logic in functional components. They provide an easy-to-use API for managing component state, executing side effects, and interacting with the component lifecycle. By using hooks, you can write more concise and readable code, as well as easily share logic between multiple components. Think of them as Lego bricks that you can use to build complex and interactive React applications.

Here's a simple example of how to use the useState hook to manage state in a functional component:

import React, { useState } from 'react';

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

  function handleClick() {
    setCount(count + 1);
  }

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={handleClick}>Click me</button>
    </div>
  );
}

In this example, we use the useState hook to declare a state variable called count and a function called setCount to update its value. We initialize count to 0 using the useState hook's argument. We then define a function called handleClick that updates the count state variable using setCount. Finally, we render the current count value and a button that triggers the handleClick function when clicked.

This was a very basic example of using a React hook. Now let's use this knowledge and use it with another React hook which is called useEffect!

here's an example of how to use the useEffect hook to execute side effects in a functional component:

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

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

  useEffect(() => {
    document.title = `You clicked ${count} times`;
  });

  function handleClick() {
    setCount(count + 1);
  }

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={handleClick}>Click me</button>
    </div>
  );
}

In this example, we use the useEffect hook to execute a side effect - updating the document title - every time the count state variable changes. We pass a function to the useEffect hook as its first argument, which will be executed after the component has rendered for the first time and every time the count variable changes. By default, useEffect runs after every render, but you can also specify dependencies to control when it should run.

React hooks like useState and useEffect make our development more efficient by allowing us to write stateful logic and execute side effects in functional components. This makes it easier to reuse and share code across multiple components, as well as reducing the amount of boilerplate code we need to write. Additionally, hooks encourage developers to write more declarative code, which is easier to read and understand than imperative code. Overall, using hooks can help us build more efficient and maintainable React applications.

Introduction To Custom React Hooks

While React provides us with tons of awesome built-in hooks, there are times when we need to build our own custom hooks to achieve certain functionality. Luckily React allows us to easily build our own hooks. But we need to follow certain rules when we're creating our own React hooks:

1. Hooks must start with the prefix use. This is a convention that tells React that the function is a hook and can be used with the useState, useEffect, and other built-in hooks.

2. Hooks must only call other hooks, or be a plain JavaScript function. You cannot call a hook inside a loop, condition or nested function. This ensures that the order of hooks is always the same, and that hooks are always called in the same order in every render.

Let's start implementing above rules in our custom hook! We are going to take the previous example and build a custom hook that combines the functionality of useState and useEffect handles and change the document's title.

import { useState, useEffect } from 'react';

function useDocumentTitle(initialCount) {
  const [count, setCount] = useState(initialCount);

  useEffect(() => {
    document.title = `You clicked ${count} times`;
  }, [count]);

  return [count, setCount];
}

In this example, we define a custom hook called useDocumentTitle that returns a state variable called count and a function called setCount, just like the useState hook. However, in addition to managing state, the useDocumentTitle hook also executes a side effect to update the document title whenever the count variable changes, just like the useEffect hook.

To use this custom hook in a component, we would import it and call it just like any other hook:

import React from 'react';
import useDocumentTitle from './useDocumentTitle';

function Example() {
  const [count, setCount] = useDocumentTitle(0);

  function handleClick() {
    setCount(count + 1);
  }

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={handleClick}>Click me</button>
    </div>
  );
}

Using custom hooks like useDocumentTitle can help us encapsulate and reuse stateful logic and side effects across multiple components, making our code more modular and easier to maintain. Additionally, it can make our components more focused and easier to reason about, as we can extract complex state management and side effect code into a separate hook.

Adding more features to our custom Hook

The above example is a very basic example of what you can do with custom React hooks, but often time you're going to build more complex hooks, you're going to handle multiple events and side effects.

Now let's add more advanced features to our useDocumentTitle to understand the React Hooks better. Let's see how we can handle multiple state variables and side effects.

import { useState, useEffect } from 'react';

function useDocumentTitleAndLocalStorage(initialCount) {
  const [count, setCount] = useState(initialCount);
  const [name, setName] = useState('');

  useEffect(() => {
    document.title = `You clicked ${count} times`;
  }, [count]);

  useEffect(() => {
    localStorage.setItem('name', name);
  }, [name]);

  function resetCount() {
    setCount(initialCount);
  }

  return { count, setCount, name, setName, resetCount };
}

In this example, we define a custom hook called useDocumentTitleAndLocalStorage that manages two state variables: count and name. We also define two side effects: one that updates the document title when the count variable changes, and another that saves the name variable to local storage when it changes.

Additionally, we define a function called resetCount that resets the count variable to its initial value. This function is returned as part of the hook's state object, along with the other state variables and functions.

To use this custom hook in a component, we would import it and call it just like any other hook:

import React from 'react';
import useDocumentTitleAndLocalStorage from './useDocumentTitleAndLocalStorage';

function Example() {
  const { count, setCount, name, setName, resetCount } = useDocumentTitleAndLocalStorage(0);

  function handleClick() {
    setCount(count + 1);
  }

  function handleNameChange(event) {
    setName(event.target.value);
  }

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={handleClick}>Click me</button>
      <input type="text" value={name} onChange={handleNameChange} />
      <p>Hello, {name}!</p>
      <button onClick={resetCount}>Reset count</button>
    </div>
  );
}

Using custom hooks like useDocumentTitleAndLocalStorage can help us manage more complex state and side effects in our components, while still adhering to the basic rules of hooks. By encapsulating reusable logic in custom hooks, we can write more modular and maintainable code, and make our development more efficient.

Conclusion

By mastering the basics of hooks and exploring advanced hook patterns and use cases, you can become a more efficient and effective React developer. So why not try creating your own custom hooks today and see what you can build?

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