Lesson 8 of 10
useEffect Hook
useEffect lets you perform side effects in components: fetching data, subscribing to events, or manually changing the DOM. It runs after the component renders.
The dependency array controls when useEffect runs. An empty array [] means "run once on mount."
REACT
import { useState, useEffect } from "react";
function UserList() {
const [users, setUsers] = useState([]);
useEffect(() => {
fetch("https://api.example.com/users")
.then(res => res.json())
.then(data => setUsers(data));
}, []); // Empty array = run once
return (
<ul>
{users.map(user => (
<li key={user.id}>{user.name}</li>
))}
</ul>
);
}