How does Rspack implement code splitting?

Code splitting is one of Rspack's important features for optimizing application performance, effectively reducing initial load time and improving user experience. Here's a detailed explanation of Rspack's code splitting:

Basic Concept of Code Splitting

Code splitting refers to splitting code into multiple bundles and loading them on demand, rather than packaging all code into one large bundle. This allows:

• Reducing the amount of code loaded initially
• Implementing on-demand loading, improving first-screen load speed
• Optimizing caching strategies and increasing resource reuse rate

Rspack Code Splitting Methods

1. Entry Points Splitting: Implement code splitting by configuring multiple entry points:

   javascript
   module.exports = {
     entry: {
       main: './src/main.js',
       vendor: './src/vendor.js'
     }
   }

2. Dynamic Import: Use import() syntax for dynamic imports:

   javascript
   // Static import
   import { add } from './math';
   
   // Dynamic import
   import('./math').then(module => {
     module.add(1, 2);
   });
   
   // Using in async functions
   async function loadModule() {
     const { add } = await import('./math');
     return add(1, 2);
   }

3. SplitChunksPlugin: Rspack has a built-in code splitting plugin that can intelligently extract common code:

   javascript
   module.exports = {
     optimization: {
       splitChunks: {
         chunks: 'all',
         cacheGroups: {
           vendors: {
             test: /[\\/]node_modules[\\/]/,
             priority: -10
           },
           default: {
             minChunks: 2,
             priority: -20,
             reuseExistingChunk: true
           }
         }
       }
     }
   }

SplitChunksPlugin Configuration Details

1. chunks:

   • all: Split all modules
   • initial: Only split initially loaded modules
   • async: Only split asynchronously loaded modules

2. minSize:

   • Minimum size of modules, modules smaller than this value will not be split
   • Default value is 30000 bytes

3. maxSize:

   • Maximum size of modules, modules larger than this value will be further split
   • Used to achieve more fine-grained code splitting

4. minChunks:

   • Minimum number of times a module is referenced
   • Default value is 1

5. maxAsyncRequests:

   • Maximum number of parallel requests when loading on demand
   • Default value is 5

6. maxInitialRequests:

   • Maximum number of parallel requests at entry points
   • Default value is 3

7. name:

   • Name of the chunk after splitting
   • Can be a string or function

Framework Integration

1. React:

   javascript
   import React, { Suspense, lazy } from 'react';
   
   const LazyComponent = lazy(() => import('./LazyComponent'));
   
   function App() {
     return (
       <Suspense fallback={<div>Loading...</div>}>
         <LazyComponent />
       </Suspense>
     );
   }

2. Vue:

   javascript
   const LazyComponent = () => import('./LazyComponent.vue');
   
   new Vue({
     components: {
       LazyComponent
     }
   });

3. Route-level Code Splitting:

   javascript
   // React Router
   const Home = lazy(() => import('./routes/Home'));
   const About = lazy(() => import('./routes/About'));
   
   // Vue Router
   const routes = [
     {
       path: '/',
       component: () => import('./views/Home.vue')
     },
     {
       path: '/about',
       component: () => import('./views/About.vue')
     }
   ];

Performance Optimization Recommendations

1. Reasonable Splitting Strategy:

   • Adjust splitting configuration based on project scale and characteristics
   • Avoid excessive splitting leading to too many HTTP requests
   • Balance bundle size and number of requests

2. Preload Critical Resources:

   javascript
   import(/* webpackPrefetch: true */ './path/to/LoginModal.js');
   import(/* webpackPreload: true */ './path/to/component.js');

3. Analyze Build Results:

   • Use Rspack's analysis tools to view bundle sizes
   • Identify modules that can be further optimized
   • Monitor code splitting effects

4. Cache Optimization:

   • Set stable chunk names for third-party libraries
   • Utilize long-term caching strategies
   • Reduce unnecessary re-downloads

Best Practices

1. Split by Functional Modules:

   • Split different functional modules into independent chunks
   • Facilitate maintenance and on-demand loading

2. Extract Common Dependencies:

   • Use SplitChunksPlugin to extract common code
   • Reduce duplicate code

3. Lazy Load Non-critical Code:

   • Use dynamic imports for non-first-screen code
   • Improve first-screen load speed

4. Monitor and Optimize:

   • Regularly analyze build results
   • Adjust splitting strategy based on actual usage
   • Continuously optimize load performance

Rspack's code splitting feature provides developers with powerful performance optimization tools. Through reasonable configuration and usage, it can significantly improve application load performance and user experience.