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You can make your own Hooks! When you have components that can be used by multiple components, we can extract that component into a custom Hook. Custom Hooks start with "use". Example: useFetch.
First, let us make an example without a custom Hook.In the following code, we are fetching data from a URL and displaying it.
JSONPlaceholder service to fetch some fake data. To learn more about fetching data, check out the
section.
Use the JSONPlaceholder service to fetch some fake titles and display them:
import { useState, useEffect } from 'react';
import { createRoot } from 'react-dom/client';const Home = () => {
const [data, setData] = useState(null);useEffect(() => {
fetch("https://jsonplaceholder.typicode.com/todos").then((res) => res.json()).then((data) => setData(data));
}, []);return (<>
{data &&
data.map((item) => {
return <p key={item.id}>{item.title}</p>;
})}</>
);
};createRoot(document.getElementById('root')).render( <Home />
);Example » The logic behind the fetch may be needed in other components as well, so we will turn that into a custom Hook. Move the fetch logic to a new file to be used as a custom Hook. The file name must start with use, and end with.js, and be placed in the same directory as the component. We will name the file useFetch.js.
Move the fetch component into the new file:
import { useState, useEffect } from "react";const useFetch = (url) => {
const [data, setData] = useState(null);useEffect(() => {
fetch(url).then((res) => res.json()).then((data) => setData(data));
}, [url]);return [data];
};export default useFetch;Now we can import this Hook, and use it in any other component:
Import and use the newly created custom Hook:
import { createRoot } from 'react-dom/client';
import useFetch from "./useFetch";const Home = () => {
const [data] = useFetch("https://jsonplaceholder.typicode.com/todos");return (<>
{data &&
data.map((item) => {
return <p key={item.id}>{item.title}</p>;
})}</>
);
};createRoot(document.getElementById('root')).render( <Home />
);Example »
We have created a new file called useFetch.js containing a function called useFetch which contains all of the logic needed to fetch our data.
Formula
We removed the hard - coded URL and replaced it with a url variable that can be passed to the custom Hook.Lastly, we are returning our data from our Hook. In main.jsx, we are importing our useFetch Hook and utilizing it like any other Hook. This is where we pass in the URL to fetch data from. Now we can reuse this custom Hook in any component to fetch data from any URL.