defineAsyncComponent function in Vue3: asynchronous loading of components

Vue3 is a very popular front-end framework that brings componentization ideas into front-end development, allowing developers to build complex applications faster and more efficiently. In Vue3, we often use components to build pages, and use a large number of third-party component libraries to extend our functionality. However, loading multiple components may cause the application to start slower, which is why we need to load components asynchronously. In Vue3, a function called defineAsyncComponent is provided, which can help us load components asynchronously to improve application performance.

What is defineAsyncComponent?

defineAsyncComponent is a function provided by Vue3, which is used to load components asynchronously. Through this function, we can separate the import and registration of components to achieve asynchronous loading of components. This function accepts a function that returns a Promise object as a parameter, and the return value of the function should be a Vue component.

Using defineAsyncComponent

Let’s take a look at how to use the defineAsyncComponent function to load components asynchronously.

First of all, where we need to use asynchronously loaded components, we need to first change the introduction of the component to asynchronous mode. For example:

import { defineAsyncComponent } from 'vue';

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

export default {
name: 'App',
components: {

AsyncComponent

},
}

Among them, the defineAsyncComponent function accepts a function that returns a Promise object as Parameters, the resolve() method of the Promise object returns the component that needs to be loaded asynchronously.

When using AsyncComponent, we no longer need to complete the registration of this component in the component as before. After defining the async component, we can now use it in our templates like any other component. For example:

Only when using AsyncComponent, the component will be downloaded from the server . Until then, the component will not be downloaded. This can greatly improve application startup time, especially in large and complex applications.

Define multiple asynchronous components

When we need to define multiple asynchronous components, we can store them in an object. For example:

import { defineAsyncComponent } from 'vue';

const asyncComponents = {
AsyncComponent1: defineAsyncComponent(() => import('./AsyncComponent1.vue')) ,
AsyncComponent2: defineAsyncComponent(() => import('./AsyncComponent2.vue')),
AsyncComponent3: defineAsyncComponent(() => import('./AsyncComponent3.vue'))
};

export default {
name: 'App',
components: asyncComponents
}

In this way, we can use these asynchronous components anywhere . For example, use in a template: