How to support on-demand loading in Vue

export default does not hinder on-demand loading. The key is how to build projects and configure packaging tools. The packaging tool automatically recognizes the import statement and divides the components according to the code segmentation configuration. To achieve on-demand loading, you need to set code splitting options in the packaging tool configuration, such as optimization.splitChunks in Webpack, to split the components into separate chunks, which are only loaded when needed.

export default and on-demand loading in Vue: Deep analysis

Many developers are puzzled when using Vue how export default works with on-demand loading. On the surface, export default exports are the default export of components, which seems to be out of place with on-demand loading. In fact, export default itself does not directly affect on-demand loading, the key is how you build your project and use packaging tools. This article will explore this seemingly contradictory issue in depth and share some practical experience.

Let's make it clear first: export default is just a way to export, and it does not itself prevent loading on demand. Implementations of loading on demand rely on configuration and modular specifications of packaging tools such as Webpack, Rollup, Vite.

Basic review: Modular and packaging tools

Modularity is essential in modern JavaScript development. export default and export are both export syntaxes for ES modules, which are used to expose components or functions to other modules for use. The packaging tool is responsible for packaging these modules into JavaScript files that are recognizable by the browser and optimized, such as code segmentation, compression, etc. It is this feature of code segmentation that makes on-demand loading possible.

Core concepts: code segmentation and on-demand loading

Code segmentation refers to splitting a large JavaScript file into multiple smaller files, loading only the code required for the current page. Loading on demand is a specific implementation of code segmentation. It only loads the corresponding code when needed, thereby improving page loading speed and performance.

export default and code segmentation work together

Suppose you have a component named MyComponent.vue :

 <code class="vue"><template> <div>This is MyComponent</div> </template> <script> export default { name: &#39;MyComponent&#39;, // ... other options } </script></code>

This component is exported using export default . When using packaging tools such as Webpack, if your configuration is correct, Webpack will automatically recognize import MyComponent from './MyComponent.vue' statement, and divide the configuration according to your code to package MyComponent.vue into a separate chunk. This chunk will only be loaded when your application requires MyComponent . Therefore, export default does not hinder on-demand loading.

In-depth implementation: Webpack configuration example

In order to achieve on-demand loading, you need to set it accordingly in the Webpack configuration, such as using the optimization.splitChunks option. A simplified example:

 <code class="javascript">// webpack.config.js module.exports = { // ... other configurations optimization: { splitChunks: { chunks: 'all', // 或者'async' 只针对异步加载的模块minSize: 0, // 尽可能小的chunk cacheGroups: { vendor: { test: /[\\/]node_modules[\\/]/, name: 'vendors', chunks: 'all' } } } } }</code>

This configuration will split all modules (including modules under node_modules ) into separate chunks to achieve on-demand loading. Note that minSize: 0 may cause many small chunks to be generated and need to be adjusted according to actual conditions.

Advanced tips: Dynamic import()

More finer on-demand loading can be implemented through import() function:

 <code class="javascript">// 在需要的时候动态加载组件const component = () => import('./MyComponent.vue') // ... 在组件中使用component().then(module => { // 使用module.default 获取组件this.MyComponent = module.default; })</code>

This method allows more precise control of the loading timing of components.

Performance optimization and best practices

• Set up the code segmentation strategy reasonably: Avoid too small chunks, otherwise it will increase the number of HTTP requests and affect performance.
• Use the right packaging tool: Choose a powerful and easy to configure package tool, such as Vite, which has faster cold start speeds.
• Optimize images and static resources: Using the right image format and compression tools can significantly reduce page loading time.
• Use code compression and obfuscation: reduce code volume and improve loading speed.

Remember, export default is just a way to export, and the implementation of loading on demand depends on the configuration of the packaging tool and your code structure. By placing and using dynamic import() properly, you can make full use of Vue's componentization features and build high-performance applications. To avoid over-optimization, finding a balance between performance and development efficiency is the key.

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