How to use keep-alive to cache dynamic components in Vue

Vue is a popular JavaScript framework for building modern web applications. One of the hallmarks of Vue is its flexibility and efficiency. Among them, keep-alive is a function provided by Vue, which is used to cache dynamic components and improve application performance. In this article, we will discuss the use of keep-alive in Vue.

What is keep-alive?

In Vue, when a component is destroyed, its state and data will also be destroyed. However, sometimes we need to preserve the state and data of a component when switching components to improve user experience and application performance. At this time, keep-alive comes into play. keep-alive is an abstract component provided by Vue for caching dynamic components and retaining their state and data when the component is switched.

Using keep-alive

Using keep-alive in Vue is very simple. We only need to wrap the components that need to be cached in the tag. For example, we have a dynamic component that uses asynchronous component technology to dynamically load:

<template>
  <div>
    <button @click="showComponentA">Show Component A</button>
    <button @click="showComponentB">Show Component B</button>
    <component :is="currentComponent"></component>
  </div>
</template>

<script>
export default {
  data() {
    return {
      currentComponent: null
    }
  },

  methods: {
    showComponentA() {
      this.currentComponent = () => import('./ComponentA.vue')
    },

    showComponentB() {
      this.currentComponent = () => import('./ComponentB.vue')
    }
  }
}
</script>

In this component, we have two buttons for switching the display of ComponentA and ComponentB components. currentComponent dynamically loads components based on button click events. Now we need to use keep-alive to cache these two components. Simply wrap the tag in the tag:

<template>
  <div>
    <button @click="showComponentA">Show Component A</button>
    <button @click="showComponentB">Show Component B</button>
    <keep-alive>
      <component :is="currentComponent"></component>
    </keep-alive>
  </div>
</template>

Now, when we switch components , the component's state and data will be retained and will not be destroyed.

Additional configuration options

In addition to simple usage, Vue also provides some configuration options to further control the behavior of keep-alive.

exclude and include

exclude and include are two Boolean properties used to control keep-alive cached components. exclude is used to specify components that need to be excluded from the cache, while include is used to specify that only specific components are cached. They are usually used with dynamic components, for example:

<template>
  <div>
    <button @click="showComponentA">Show Component A</button>
    <button @click="showComponentB">Show Component B</button>
    <keep-alive :exclude="['ComponentA']">
      <component :is="currentComponent"></component>
    </keep-alive>
  </div>
</template>

In this example, we use the exclude attribute to exclude the ComponentA component, so it will not be cached.

max and min

max and min are two numeric attributes used to control the maximum and minimum number of dynamic components in the keep-alive cache. When the maximum is exceeded, the oldest unused components will be destroyed until the number of cached components reaches the minimum. For example:

<template>
  <div>
    <button @click="showComponentA">Show Component A</button>
    <button @click="showComponentB">Show Component B</button>
    <keep-alive :max="5" :min="2">
      <component :is="currentComponent"></component>
    </keep-alive>
  </div>
</template>

In this example, we use the max attribute to specify a maximum cache of 5 components, and the min attribute to specify a minimum cache of 2 components.

Conclusion

keep-alive is a very powerful feature provided by Vue that can help us improve the performance and user experience of our application. In this article, we introduced how to use keep-alive in Vue to cache dynamic components and discussed some additional configuration options. Now we can manage component state and data more efficiently in Vue applications.

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