What is React - Quick Revision & Key Takeaways

Recall & Review

beginner

What is React?

React is a JavaScript library used to build user interfaces, especially for web apps. It helps create reusable components that update efficiently when data changes.

beginner

What is a React component?

A React component is a small, reusable piece of code that returns HTML-like elements to show on the screen. Components can be functions or special JavaScript classes.

beginner

Why do we use React?

We use React to build fast and interactive user interfaces. It updates only the parts of the page that change, making apps feel quick and smooth.

beginner

What is JSX in React?

JSX is a syntax that looks like HTML but works inside JavaScript. It lets you write UI code that React can understand and turn into real web page elements.

intermediate

How does React update the UI efficiently?

React uses a virtual copy of the UI called the virtual DOM. It compares changes there first, then updates only the real parts that need to change, saving time and resources.

What is React mainly used for?

A Building user interfaces

B Managing databases

C Styling web pages

D Writing server code

React is a library focused on building user interfaces, not databases or server code.

What does JSX allow you to do in React?

A Write CSS styles directly

B Write HTML-like code inside JavaScript

C Create server endpoints

D Manage databases

JSX lets you write HTML-like syntax inside JavaScript to describe UI elements.

How does React improve performance when updating the UI?

A By using a virtual DOM to update only changed parts

B By disabling user interactions

C By running code on the server only

D By updating the entire page every time

React uses a virtual DOM to find and update only the parts of the UI that changed.

Which of these is a React component?

A A CSS style rule

B A database table

C A reusable piece of UI code

D A server configuration

React components are reusable pieces of code that define parts of the UI.

React is best described as:

A A full web framework

B A CSS framework

C A database system

D A JavaScript library for UI

React is a JavaScript library focused on building user interfaces, not a full framework or database.

Explain what React is and why it is useful for building web apps.

Think about how React helps with building parts of a web page that change often.

Describe how React uses JSX and the virtual DOM to create fast user interfaces.

Focus on how React writes UI code and updates the screen quickly.