ReactJS Features: JSX, Components, Hooks & Virtual DOM

Core Features of ReactJS

What Are React's Core Features?

These are the ideas that make React what it is. You do not need to master them now just recognise the names.

1. Component-Based Architecture

The UI is split into independent components that can be nested and reused.

2. JSX

A syntax that lets you write UI structure inside JavaScript files. Covered fully in Module 3.

3. Virtual DOM

React keeps a lightweight copy of the page structure in memory. When data changes, it compares the new version against the old one, works out the minimum set of changes, and applies only those to the real page.

4. One-Way Data Flow

Data flows from parent components down to child components through props. A child cannot directly change its parent's data. This sounds restrictive but makes bugs far easier to trace when a value is wrong, you follow it upward to exactly one source.

5. Hooks

Functions like useState and useEffect that let components hold data and run side effects. Covered in Modules 5 and 7.

6. Declarative UI

You describe the result you want, not the steps to get there.

// Declarative: describe what should show

{isLoggedIn ? <Dashboard /> : <LoginForm />}

Compare this with the imperative approach in plain JavaScript, where you would manually create, remove, and hide elements.