Hot Module Replacement (HMR)

1. Introduction

Hot Module Replacement (HMR) is a feature of webpack that allows modules to be updated at runtime without a full refresh. This leads to a better development experience by preserving application state, enabling developers to see changes instantly.

2. Key Concepts

3. Setup

To enable HMR, follow these steps:

1. Install webpack and webpack-dev-server:

npm install --save-dev webpack webpack-cli webpack-dev-server

2. Add HMR configuration in your webpack.config.js:

const webpack = require('webpack');

module.exports = {
  // Other configurations...
  devServer: {
    contentBase: './dist',
    hot: true, // Enable HMR
  },
};
            

3. Include the HMR client in your entry point:

entry: [
  'webpack/hot/dev-server',
  './src/index.js'
],

4. Workflow

The HMR workflow can be visualized as follows:

graph TD;
    A[Start Development] --> B{Code Change?};
    B -- Yes --> C[Update Module];
    C --> D[Preserve State];
    D --> E[Render Changes];
    B -- No --> A;
        

5. Best Practices

To make the most of HMR:

• Keep your modules small and focused for better performance.
• Use HMR only in development mode to avoid production issues.
• Test changes frequently to catch integration issues early.

6. FAQ