Optimizing Vue.js Performance: A Guide to Tree Shaking with Webpack and Vite
Tags: vue, javascript, tutorial
Published: 2023-11-08 20:45:58

When building Vue.js applications, efficiency and performance are one of the keys. Webpack and Vite are two prominent tools in the modern web development toolkit. They offered a feature known as tree shaking, it is a method to clean up your final code bundle by removing unused JavaScript. Here’s how you can ensure your Vue.js codebase is primed for tree shaking with these tools.

## Optimizing Vue.js with Webpack

Webpack has supported tree shaking since version 2. For Vue.js developers, this means you can eliminate dead code and optimize your app's performance by following some best practices:

1. **Use ES2015 Module Syntax** 
Vue.js components should use `import` and `export` to leverage Webpack’s static analysis capabilities.

    ```javascript
    // Example of importing a specific function from a utility file
    import { calculateTax } from './utils/tax';
    ```

2. **Set Webpack to Production Mode**
Ensure your `webpack.config.js` specifies `mode: 'production'`, which activates tree shaking among other optimizations.

    ```javascript
    module.exports = {
      mode: 'production',
      // ... other configurations
    };
    ```

3. **Control Side Effects in `package.json`**
Mark your pure modules as side-effect-free.

    ```json
    "sideEffects": ["*.vue", "*.css"]
    ```

4. **Proper Babel Configuration**
Do not transpile ES2015 module syntax to CommonJS, as this will disable tree shaking.

    ```json
    {
      "presets": [
        ["@babel/preset-env", { "modules": false }]
      ]
    }
    ```

## Optimizing Vue.js with Vite

Vite, a newer and faster build tool, embraces tree shaking by default for production builds, harnessing the power of Rollup under the hood. To get the most out of Vite’s capabilities:

1. **Follow Standard Import and Export Practices**
Vite will handle tree shaking automatically if you use standard ES modules.

    ```javascript
    // Import only what you need in your Vue.js component
    import { ref } from 'vue';
    ```

2. **Analyze Your Bundle**
Use Vite’s build analysis feature to check the contents of your final bundle.

    ```shell
    vite build --report
    ```

3. **Efficient Component Importing**
Utilize dynamic imports for Vue components in routes or large components to split code and load it when needed.

    ```javascript
    const UserSettings = () => import('./components/UserSettings.vue');
    ```

## Optimizing a Vue.js Component

Here's an example of a Vue.js component optimized for tree shaking:

```javascript
<template>
  <div>
    <h1>Tax Calculator</h1>
    <p>Total: {{ totalWithTax }}</p>
  </div>
</template>

<script>
import { calculateTax } from './utils/tax';
import { ref } from 'vue';

export default {
  name: 'TaxCalculator',
  setup() {
    const amount = ref(1000);
    const totalWithTax = ref(calculateTax(amount.value));

    return {
      totalWithTax
    };
  }
};
</script>
```

In the example above, we're importing only what we need (`calculateTax` and `ref`). The rest of the unused exports from **tax.js** and **vue** would be remove in the final bundle when using either Webpack or Vite in production mode.

By following these guidelines and employing tree shaking, your Vue.js applications built with Webpack or Vite will be leaner and faster. 

Remember, the key to successful tree shaking lies in how you structure your code and the build configurations you set. With a little attention to detail, you can see significant improvements in your application's performance.

#### Enjoy!