Use Vue's keep-alive component to implement page cache update strategy

Use Vue’s keep-alive component to implement page cache update strategy

Introduction:
When developing web applications, it is often necessary to deal with page cache and update strategies. Based on Vue's SPA (Single-Page Application) application, we can use Vue's keep-alive component to control page caching and updates. This article will introduce how to use Vue's keep-alive component to implement the page cache update strategy and provide corresponding code examples.

1. What is the Keep-alive component?
Vue's keep-alive component is an abstract component used to cache components. It can cache the component before it is destroyed so that it can be read directly from the cache when the component is rendered again, thus improving the page loading speed and user experience.

2. How to use Keep-alive
Using keep-alive is very simple, just wrap the component to be cached in the tag.

<template>
  <div>
    <keep-alive>
      <!-- 缓存的组件放在这里 -->
    </keep-alive>
  </div>
</template>

3. Keep-alive caching strategy

1. include attribute: Specify the component name or component instance that needs to be cached. Only components specified by include will be cached.

<template>
  <div>
    <keep-alive :include="['ComponentA', ComponentB]">
      <router-view></router-view> <!-- 嵌套路由视图 -->
    </keep-alive>
  </div>
</template>

2. exclude attribute: Specify the component name or component instance that does not need to be cached. Components specified by exclude will not be cached.

<template>
  <div>
    <keep-alive :exclude="['ComponentC', ComponentD]">
      <router-view></router-view> <!-- 嵌套路由视图 -->
    </keep-alive>
  </div>
</template>

3. max attribute: Specifies the maximum number of cached components. When the number of cached components exceeds the number specified by max, the first cached component will be destroyed.

<template>
  <div>
    <keep-alive :max="10">
      <router-view></router-view> <!-- 嵌套路由视图 -->
    </keep-alive>
  </div>
</template>

4. Keep-alive update strategy
By default, cached components will not be re-rendered when routing is switched. If we need to re-render cached components when routing switches, we can use the following strategy.

1. Changes in the internal state of the component
   When the internal state of the component changes, the current component will be re-rendered.

export default {
  data() {
    return {
      count: 0
    };
  },
  methods: {
    increment() {
      this.count++;
    }
  }
};

2. Declare the beforeRouteUpdate hook function
   Declare the beforeRouteUpdate hook function in the component. When the route is switched, the cached component will call the hook function.

export default {
  data() {
    return {
      count: 0
    };
  },
  methods: {
    increment() {
      this.count++;
    }
  },
  beforeRouteUpdate(to, from, next) {
    next();
  }
};

In the beforeRouteUpdate hook function, we can decide whether to re-execute certain logic based on the different conditions of the to and from parameters. For example, operations such as re-obtaining data are required when routing is switched.

5. Sample code
The following is a sample code that uses Vue’s keep-alive component to implement the page cache update strategy:

<template>
  <div>
    <keep-alive :include="['ComponentA', 'ComponentB']">
      <router-view></router-view>
    </keep-alive>
  </div>
</template>

<script>
export default {
  data() {
    return {
      count: 0
    };
  },
  methods: {
    increment() {
      this.count++;
    }
  },
  beforeRouteUpdate(to, from, next) {
    this.count = 0; // 路由切换时重置count为0
    next();
  }
};
</script>

6. Summary
Using Vue’s keep- The alive component can easily implement page caching and update strategies. We can control the components that need to be cached through the include and exclude attributes, and the number of cached components through the max attribute. By default, cached components will not be re-rendered, but components can be re-rendered through changes in the component's internal state and the beforeRouteUpdate hook function.

I hope that through the introduction of this article, you can better understand and apply Vue's keep-alive component to improve page loading speed and user experience.

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