Lazy Loading | Intermediate Vuejs

Lazy Loading Components and Routes

Lazy loading is a technique that allows you to load components and routes only when they are needed, improving the initial load time and overall performance of your VueJS applications. This guide covers how to implement lazy loading for components and routes in VueJS.

Key Points:

Lazy loading improves initial load time by splitting your application into smaller chunks.
VueJS supports lazy loading for both components and routes out of the box.
Dynamic imports are used to implement lazy loading.

Lazy Loading Components

To lazy load a component, use the dynamic import() syntax:


// MyComponent.vue




// ParentComponent.vue

Lazy Loading Routes

To lazy load routes, use the dynamic import() syntax in your router configuration:


// router/index.js
import Vue from 'vue';
import Router from 'vue-router';

Vue.use(Router);

const routes = [
  {
    path: '/home',
    component: () => import('@/components/Home.vue')
  },
  {
    path: '/about',
    component: () => import('@/components/About.vue')
  }
];

const router = new Router({
  routes
});

export default router;

Preloading and Prefetching

Vue CLI supports preloading and prefetching for better performance. Preloading ensures that critical assets are loaded as soon as possible, while prefetching loads assets during idle time:


// vue.config.js
module.exports = {
  chainWebpack: config => {
    config.plugin('prefetch').tap(options => {
      options[0].fileBlacklist = options[0].fileBlacklist || [];
      options[0].fileBlacklist.push(/myasyncRoute(.)+?\.js$/);
      return options;
    });
    config.plugin('preload').tap(options => {
      options[0].fileWhitelist = options[0].fileWhitelist || [];
      options[0].fileWhitelist.push(/myasyncRoute(.)+?\.js$/);
      return options;
    });
  }
};

Handling Loading States

While waiting for a component or route to load, you can display a loading state to improve user experience:


// ParentComponent.vue

Best Practices

Follow these best practices when implementing lazy loading in VueJS:

Identify Critical Paths: Lazy load only non-critical components and routes to ensure that critical paths load quickly.
Use Loading States: Provide visual feedback to users while waiting for components or routes to load.
Test Performance: Test the performance of your application to ensure that lazy loading is improving load times and user experience.
Combine with Code Splitting: Combine lazy loading with code splitting to further improve the performance of your application.
Monitor Bundle Sizes: Monitor the sizes of your bundles to ensure that they remain manageable and optimized.

Summary

This guide provided an overview of lazy loading components and routes in VueJS, including how to implement lazy loading using dynamic imports, handling loading states, and best practices. By understanding and utilizing these techniques, you can improve the performance and user experience of your VueJS applications.

VueJS - Lazy Loading