# import {useEffect} from "react";
The statement `import {useEffect} from "react";` is a JavaScript import declaration used in React applications.
**Purpose: **
This line imports the `useEffect` Hook from the React library. The `useEffect` Hook is a fundamental part of functional components in React, enabling developers to perform "side effects."
**Side Effects in React: **
Side effects are operations that interact with the outside world or have an impact beyond the component's render cycle. Common examples of side effects include:
- **Data fetching:** Making API calls to retrieve data from a server. - **DOM manipulation:** Directly interacting with the browser's Document Object Model (e.g., setting the document title). - **Subscriptions:** Setting up event listeners or connecting to external services like WebSockets. - **Timers:** Using `setTimeout` or `setInterval`.
**How `useEffect` Works: **
**`useEffect` takes two arguments: **
-
**A setup function:**
This function contains the code for your side effect. It runs after every render of the component (including the initial render) unless its dependencies prevent it from doing so.
-
**A dependency array (optional):**
This array specifies the values that the effect depends on. If any of these values change between renders, the effect will re-run. An empty dependency array `[]` ensures the effect runs only once after the initial render (similar to `componentDidMount` in class components).
Example Usage:
``` import { useEffect, useState } from "react"; function MyComponent() { const [count, setCount] = useState(0); useEffect(() => { // This side effect updates the document title document.title = `Count: ${count}`; }, [count]); // The effect re-runs whenever 'count' changes return (

Count: {count}

); } export default MyComponent; ```