Vue.js 3.0 Tutorial

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Vue 3.0 Style Guide

Vue 3.0 Async Components

Vue 3.0 offers an improved way of handling asynchronous components which makes it a lot easier to deal with components that need to be loaded on demand.

An asynchronous component is defined as a factory function that returns a Promise (which should resolve to a component). Async components can be very useful when you want to split your app into smaller chunks and load them only when necessary, improving the initial load time of your application.

Here is a simple example of defining an async component:

import { defineAsyncComponent } from 'vue'

const MyComponent = defineAsyncComponent(() =>
  import('./MyComponent.vue')
)

When MyComponent is used in a template, Vue will automatically handle the asynchronous loading of the component file.

Async components can also have a custom loading state, error state, delay before showing the loading indicator, and a timeout for when to give up trying to load the component.

import { defineAsyncComponent } from 'vue'

const MyComponent = defineAsyncComponent({
  loader: () => import('./MyComponent.vue'),
  loadingComponent: 'LoadingComponent',
  errorComponent: 'ErrorComponent',
  delay: 200, // default: 200ms
  timeout: 3000 // default: Infinity
})

loader: A function returning the import() function for your component.
loadingComponent: A component to be displayed while the async component is loading.
errorComponent: A component to be displayed if the load fails.
delay: The delay in ms before showing the loadingComponent.
timeout: The timeout in ms for giving up on loading the async component and showing the error component.

If the loading takes more than 200ms, the LoadingComponent will be shown. If the loading takes more than 3 seconds, or fails, the ErrorComponent will be shown.

This feature allows you to improve the user experience of your application by providing feedback to the user about what's happening, and it can also help you debug issues with loading components.

Vue 3.0 Dynamic Imports for Async Components:
- Use dynamic imports to load components asynchronously.
- Leverage import() syntax for dynamic imports.
```
const AsyncComponent = () => import('./AsyncComponent.vue');

export default {
  components: {
    AsyncComponent,
  },
};
```
Using Vue 3.0 Lazy-Loading with Async Components:
- Lazy-load components only when needed.
- Improve initial page load performance.
```
const LazyComponent = () => import('./LazyComponent.vue');

export default {
  components: {
    LazyComponent,
  },
};
```
Vue 3.0 Async Component Loading Strategies:
- Choose loading strategies based on the use case.
- Async components can be loaded on demand or in the background.
```
const BackgroundLoadedComponent = () => import(/* webpackChunkName: "background-loaded" */ './BackgroundLoadedComponent.vue');
```
Vue 3.0 Async Components with Webpack Code Splitting:
- Leverage Webpack's code splitting for efficient async loading.
- Use comments to name the chunks for better debugging.
```
const AsyncComponent = () => import(/* webpackChunkName: "async-component" */ './AsyncComponent.vue');
```
Vue 3.0 Async Component Caching:
- Vue 3.0 automatically caches async components.
- Subsequent requests for the same async component reuse the cached version.
```
const CachedComponent = () => import('./CachedComponent.vue');
```

Handling Errors with Vue 3.0 Async Components:

Implement error handling for failed component loading.
Use the errorCaptured lifecycle hook.

const AsyncComponent = () => import('./AsyncComponent.vue');

export default {
  components: {
    AsyncComponent,
  },
  errorCaptured(err, vm, info) {
    console.error('Error in async component:', err, vm, info);
  },
};

Vue 3.0 Async Components and Suspense:

Combine async components with Vue 3.0 Suspense.
Provide fallback content while components are loading.

<suspense>
  <template #default>
    <async-component></async-component>
  </template>
  <template #fallback>
    <p>Loading...</p>
  </template>
</suspense>

Vue 3.0 Async Components in Routing:
- Integrate async components with Vue Router.
- Lazy-load route components for better performance.
```
const Home = () => import('./Home.vue');

const routes = [
  { path: '/', component: Home },
];
```

Vue 3.0 Async Components and SSR (Server-Side Rendering):

Consider SSR implications when using async components.
Ensure proper handling of async components during server-side rendering.

const AsyncComponent = () => import('./AsyncComponent.vue');

export default {
  asyncData() {
    // Fetch data needed for the component during SSR
  },
  components: {
    AsyncComponent,
  },
};

Vue 3.0 Async Components and Reactivity:

Async components seamlessly integrate with Vue 3.0 reactivity.
Leverage reactivity features within async components.

const ReactiveComponent = () => import('./ReactiveComponent.vue');

export default {
  components: {
    ReactiveComponent,
  },
  data() {
    return {
      message: 'Hello from parent',
    };
  },
};

Vue 3.0 Async Component Examples:

Lazy-Loaded Modal:

const Modal = () => import('./Modal.vue');

export default {
  methods: {
    openModal() {
      Modal().then((mod) => {
        this.$modal.open(mod.default);
      });
    },
  },
};

Background-Loaded Analytics Component:

const Analytics = () => import(/* webpackChunkName: "analytics" */ './Analytics.vue');

Conditional Loading with User Permissions:

const AdminPanel = () => {
  if (userHasAdminPermission()) {
    return import('./AdminPanel.vue');
  } else {
    return Promise.resolve(null);
  }
};