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Vue.js is a popular front-end framework that provides some convenient functions to optimize performance and improve development efficiency. One of these features is keep-alive
, which helps us retain state between components, thereby reducing unnecessary renderings and requests. This article will introduce in detail how keep-alive
works and how to use it, and provide some code examples.
keep-alive
worksIn Vue.js, whenever we switch components, the components will be recreated and rendered. This means that every time you switch a component, the component's state is reset and the data needs to be reloaded. For some relatively stable components, this behavior can lead to unnecessary waste of performance.
And keep-alive
The role of the component is to cache components that need to retain their state instead of destroying and recreating them. This way, when switching components, if the component is already cached, it will read the state directly from the cache instead of reloading the data and rendering.
keep-alive
works as follows:
vm. $el
(the root DOM element of the component instance) is removed from the DOM tree. vm.$el
of the original component will be put into an array named _inactive
and saved. vm.$el
of the original component will be taken out from the _inactive
array and reinserted into the DOM tree. It should be noted that since the component is cached, the component's life cycle hook function (such as created
, mounted
, etc.) is only loaded for the first time It is triggered once when switching, and will not be triggered again during subsequent switching.
keep-alive
In Vue.js, we can use the 7c9485ff8c3cba5ae9343ed63c2dc3f7
component to wrap Components that need to be cached. Here are some common usages:
<template> <div> <keep-alive> <Component></Component> </keep-alive> </div> </template>
In this example, the 9366e37985177da7839522e36133b6c8
component will be cached stand up. When switching to another component and back again, 9366e37985177da7839522e36133b6c8
the component will read the state from the cache instead of recreating it.
<template> <div> <keep-alive> <router-view></router-view> </keep-alive> </div> </template>
In this example, all components loaded through the routing configuration will be cached. When switching routes, already loaded components will read their state from the cache.
<template> <div> <keep-alive :include="includeComponents"> <router-view></router-view> </keep-alive> </div> </template> <script> export default { data() { return { includeComponents: ['ComponentA', 'ComponentB'] } } } </script>
In this example, only components contained in the includeComponents
array will be cached. Other components will be destroyed and recreated when switching.
<template> <div> <keep-alive :exclude="excludeComponents"> <router-view></router-view> </keep-alive> </div> </template> <script> export default { data() { return { excludeComponents: ['ComponentA'] } } } </script>
In this example, components in the excludeComponents
array will not be cached. This means that after switching to other components, and then switching back, the excluded components will be recreated.
keep-alive
The component is a function provided by Vue.js that can help us optimize performance. It works by caching components that need to retain their state, and loading the state directly from the cache when switching, avoiding unnecessary re-rendering and requests. The method of use is simple, you can cache a single component, multiple components, and even dynamically control the cached components.
By rational use of keep-alive
components, we can improve application performance and reduce unnecessary resource consumption. I hope this article will help you understand how keep-alive
works and how to use it. If you have any questions, please feel free to leave a message to discuss.
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