Understanding HMR with React and Vite

1. Introduction

Brief Explanation of the Tutorial's Goal

This tutorial aims to provide an understanding of Hot Module Replacement (HMR) and its utilization with React and Vite. HMR is a significant feature in modern web development that enables instant updates without a full page refresh.

What the User Will Learn

By the end of this tutorial, you will understand what HMR is, how it works with React and Vite, and how it can enhance your development experience.

Prerequisites

Basic knowledge of JavaScript, React, and development setup with Vite is required.

2. Step-by-Step Guide

Hot Module Replacement (HMR) is a feature to inject updated modules into the active runtime. It's like live-reloading but without losing the current state of the app.

Vite is a modern front-end build tool that significantly improves the development experience. It's fast because it uses native ES modules for development, and has built-in HMR for modules federation.

HMR with React and Vite

React Fast Refresh is a HMR feature for React that only updates components you've changed without losing their state. Vite has built-in support for Fast Refresh.

When you save a file while running a Vite development server, Vite sends an update notification to the page, downloads the updated module, then propagates the update to all modules that import it.

Best Practices and Tips

• Keep your components small to make the most of HMR.
• Use named exports for components, which is better for Fast Refresh.
• You shouldn't rely on HMR for application logic, it's only a development feature.

3. Code Examples

Let's create a new React project with Vite and see HMR in action.

1. Create a new project:

# Create new project
npx create-vite my-app --template react

1. Run the development server:

# Go to project directory
cd my-app

# Run server
npm run dev

1. Now, go to App.jsx and change something:

function App() {
  return <h1>Hello Vite + React!</h1>; // Change this text
}

You'll notice the changes take effect immediately in your browser without a full page refresh.

4. Summary

We've learned what HMR is, how it's used in React with Vite, and some good practices. Understanding HMR can greatly improve your development experience.

Next, you can explore more about Vite and its features such as CSS code splitting, assets import, and deployment.

5. Practice Exercises

1. Try to create a new Vite project with a template other than React and observe the HMR.
2. Create multiple components in a React + Vite app and observe the HMR behavior.

Remember, the key to mastering HMR, like any other concept, is through continuous practice and implementation. Happy coding!