Understanding React Components and the Virtual DOM

As developers, we aim to build fast, scalable, and maintainable web applications. Over time, we’ve tried various frameworks and libraries, but React has truly changed the way we structure our UI logic—thanks to two of its most powerful features: components and the Virtual DOM.

In this blog, we’ll break down what React components are, how the Virtual DOM works, and why this combination makes React a go-to choice for modern frontend development.

What Are React Components?

In React, components are the building blocks of our user interfaces. Instead of thinking in terms of HTML pages, we build small, reusable pieces of code that describe a part of the UI. These pieces, or components, can be functional or class-based, and they help us write clean and modular code.

import React from 'react';

function Welcome(props) {
  return <h1>Hello, {props.name}!</h1>;
}

export default Welcome;

We can use this like:

<Welcome name="Alice" />

Types of Components

React offers two main ways to define components:

1. Functional Components (Modern and Preferred)

const Button = ({ label }) => {
  return <button>{label}</button>;
};

2. Class Components (Older Syntax)

import React, { Component } from 'react';

class Button extends Component {
  render() {
    return <button>{this.props.label}</button>;
  }
}

What is the Virtual DOM?

Let’s face it: working directly with the real DOM is slow. Every time a change happens in the UI, updating the DOM manually can lead to performance bottlenecks. This is where React’s Virtual DOM steps in.

How It Works:

When we write our components, React creates a Virtual DOM, which is just a lightweight JavaScript representation of the actual DOM.
When state or props change, React re-renders the Virtual DOM.
React then uses a process called reconciliation to diff the new Virtual DOM with the previous one.
It calculates the minimal number of changes needed to update the real DOM—and applies them efficiently.

This entire process is fast because JavaScript operations (like comparing two objects) are much quicker than direct DOM manipulation.

The Virtual DOM is what makes React apps feel snappy and responsive. By avoiding unnecessary DOM updates, React optimizes rendering and keeps performance in check, even in complex applications.

In simple terms, it’s like having a smart assistant who figures out the smallest, most efficient way to tidy up a messy room—without moving everything around unnecessarily.

Putting It All Together

import React, { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>You clicked {count} times.</p>
      <button onClick={() => setCount(count + 1)}>Click Me</button>
    </div>
  );
}

Every time we click the button:

The state (count) updates
The Virtual DOM gets re-rendered
React figures out that only the text in <p> has changed
It updates just that part of the real DOM

Final Thoughts

By embracing components and relying on the Virtual DOM, React gives us a structured, efficient way to build UIs. As our apps grow, these concepts become even more valuable, helping us keep things maintainable and fast.

Lakshyajeet.