Detailed explanation of lazy function in Vue3: Application of lazy loading components to improve application performance

In Vue3, using lazy loading components can significantly improve application performance. Vue3 provides lazy function for loading components asynchronously. In this article, we will learn more about how to use the lazy function and introduce some application scenarios of lazy loading components.

The lazy function is one of the built-in functions in Vue3. When using the lazy function, Vue3 will not load the component during the initial rendering, but will load it when the component is needed. This means that the component's code is not downloaded when the page is initially loaded, improving loading speed and performance of the entire application.

The use of lazy function is very simple. Just introduce the components that need to be lazy loaded as follows:

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

In the above code, we use the arrow function syntax of ES6 to define a MyComponent component, and use the import statement to import it from the same directory. Asynchronous import in MyComponent.vue file. This way, the component's code won't be downloaded and compiled until it's actually needed.

In addition to using arrow functions, we can also use the special syntax provided by Vue to define components. For example:

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

When using the defineAsyncComponent function to define a component, we only need to pass the path of the component file that needs to be loaded asynchronously as a parameter to the import function. Vue will automatically recognize that the object returned by this function is an asynchronous component and load it when needed.

In addition to the above usage methods, we can also define asynchronous components through the createAsyncComponent function:

const MyComponent = createAsyncComponent({
  // 異步加載的組件
  loader: () => import('./MyComponent.vue'),
  // 加載時的占位符
  loadingComponent: Loading,
  // 加載失敗時的占位符
  errorComponent: Error,
  // 加載超時時間
  delay: 200,
  // 最大重試次數(shù)
  retry: 3
})

In the above code, we create an asynchronous component through the createAsyncComponent function. This function receives an object as a parameter, which contains other options such as asynchronous loading of components, placeholders when loading, placeholders when loading fails, loading timeout, maximum number of retries, etc.

Using lazy loading components can help us optimize page performance and user experience. The following are some common application scenarios for lazy loading components:

1. Image lazy loading

Images are one of the main factors that affect page loading speed. In order to improve page loading speed and performance, we can use image lazy loading technology. Lazy loading of images can be easily achieved using lazy loading components. Just add an img tag to the component and set its src attribute to the .lazy directive:

<img v-lazy="imgUrl">

In the above code, we use the lazy directive provided by Vue3 to implement lazy loading of images. The src attribute of the image will not be set until it appears on the screen. Images are loaded and displayed only when the user scrolls the page.

2. Component lazy loading

When an application contains a large number of components, if each component is loaded in its entirety during the initial render, it will cause the page to load slowly. . To avoid this, we can use lazy loading of components. A component is loaded when the user needs it, improving overall application performance and loading speed. We can use the lazy function introduced above to implement lazy loading of components.

3. Route lazy loading

When using Vue Router, we can also use route lazy loading to further optimize page performance. When a user accesses a route, only the components required for that route are loaded and rendered. This means that for some routes users may never access them, and their associated components will never be loaded and rendered. This can significantly reduce the initialization load of the application and improve the performance of the application.

In short, using the lazy function can easily implement lazy loading of components, thereby improving application performance and user experience. We can apply it in multiple scenarios such as lazy loading of images, lazy loading of components, and lazy loading of routes. I hope this article will help you understand the application scenarios of lazy functions and lazy loading components in Vue3!

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