React: How to create a Custom Hook
Tags: react, abotwrotethis
Published: 2023-04-03 06:12:02

React is a popular JavaScript library used for building user interfaces. One of the most powerful features in React is its ability to create reusable components. However, there are times when you need to share logic between components that is not related to rendering. This is where custom hooks come in.

In this blog post, you will learn what custom hooks are, how they work, and how to create your own.

## What is a Custom Hook?

In React, a hook is a function that lets you “hook into” React state and lifecycle features from function components. Custom hooks allow you to extract logic from a component, encapsulate it into a reusable function, and share it among different components.

A custom hook is just a regular JavaScript function that uses one or more built-in React hooks to create a piece of reusable functionality. Custom hooks are named with “use” in the beginning and define a specific behavior or feature that can be used throughout your application.

## Why Use Custom Hooks?

Custom hooks provide a way to extract reusable logic from your components, making your code more modular and easier to read. They allow you to avoid duplicating code between your components and reduce the amount of state that needs to be managed. Additionally, by separating logic from rendering, you can make your application more testable and easier to maintain.

## How Do Custom Hooks Work?

Custom hooks work by using other built-in React hooks to provide reusable functionality. When you create a custom hook, you are essentially defining a new function that can take any inputs, much like any other function. However, custom hooks should be designed to use the built-in React hooks that manipulate state, so it can be used across different components.

For instance, if you have a hook that handles fetching data from an API, it could have the following code:

```
import { useState, useEffect } from "react";

function useApiData(apiUrl) {
  const [data, setData] = useState([]);
  const [isLoading, setIsLoading] = useState(false);
  const [hasError, setHasError] = useState(false);

  useEffect(() => {
    const fetchData = async () => {
      setIsLoading(true);
      try {
        const response = await fetch(apiUrl);
        const data = await response.json();
        setData(data);
      } catch (error) {
        setHasError(true);
      } finally {
        setIsLoading(false);
      }
    };
    fetchData();
  }, [apiUrl]);

  return {
    data,
    isLoading,
    hasError,
  };
}
```

Here, we used the useState and useEffect hooks to create a new hook that fetches data from an API. It sets the initial state values and updates them when the request is completed or has an error.

To use this custom hook in a component, you would do the following:

```
import { useApiData } from "./useApiData";

function MyComponent() {
  const apiUrl = "https://myapi.com/data";
  const { data, isLoading, hasError } = useApiData(apiUrl);

  if (isLoading) {
    return <div>Loading data...</div>;
  }

  if (hasError) {
    return <div>An error has occurred.</div>;
  }

  return (
    <div>
      {data.map((item) => (
        <div key={item.id}>
          <h3>{item.title}</h3>
          <p>{item.body}</p>
        </div>
      ))}
    </div>
  );
}
```

In this example, we import the useApiData hook from a separate file and pass the API URL as an argument. The hook then returns an object with the data, loading state, and error state. We can then use this object to render the component.

## How to Create a Custom Hook

Now that you understand what custom hooks are and how they work, let's go over how to create one. Here are the steps to follow:

### Step 1: Choose a Name

Your custom hook should have a clear and descriptive name that starts with the word “use”. This makes it clear that it is a hook that can be used in function components.

### Step 2: Define the Function

Next, define the function that will be used as your custom hook. This function can take any parameters you need and should be designed to use built-in React hooks to create reusable functionality.

### Step 3: Use Built-In React Hooks

Inside the function, use built-in React hooks to create the desired behavior or feature. You can use any hooks you need, including useState, useEffect, useMemo, and useCallback.

### Step 4: Return the Value

Finally, return the value that you want the hook to provide. This can be a single value, an array of values, or an object with multiple values.

Here is an example of a custom hook that provides a random number generator:

```
import { useState } from "react";

function useRandomNumber() {
  const [number, setNumber] = useState(null);

  const generateRandomNumber = () => {
    const randomNumber = Math.floor(Math.random() * 10);
    setNumber(randomNumber);
  };

  return [number, generateRandomNumber];
}
```

This custom hook uses the useState hook to create a state variable for the random number and a function to generate the number. When the function is called, it generates a random number between 0 and 10 and sets the state variable to that value. The hook then returns an array with the current value of the number and the function to generate a new number.

Here is how you would use this custom hook in a component:

```
import { useRandomNumber } from "./useRandomNumber";

function MyComponent() {
  const [number, generateRandomNumber] = useRandomNumber();

  return (
    <div>
      <h3>Random Number: {number}</h3>
      <button onClick={generateRandomNumber}>Generate New Number</button>
    </div>
  );
}
```

In this example, we import the useRandomNumber hook from a separate file and use it to generate a random number when the button is clicked. The hook returns an array with the current number and the function to generate a new number. We can then use this array in our component to display the current number and update it when the button is clicked.

## Conclusion

Custom hooks are a powerful feature in React that allow you to extract reusable logic from your components and share it between different parts of your application. With custom hooks, you can make your code more modular, easier to read, and maintainable. By following the steps outlined in this post, you can create your own custom hooks and start using them in your React applications today.