Vue <KeepAlive> Component

Welcome to The Coding College! In this guide, we’ll explore the <KeepAlive> component in Vue, a powerful tool for optimizing performance by caching inactive component instances. This component is particularly useful for improving the user experience in applications with dynamic navigation or frequently used views.

What is the <KeepAlive> Component?

The <KeepAlive> component is a wrapper in Vue that caches dynamic components when they are not active. When the component is revisited, it reuses the cached instance rather than re-rendering it from scratch.

Why Use <KeepAlive>?

1. Preserve Component State: Retains form inputs, scroll positions, or other states when switching between views.
2. Boost Performance: Prevents re-initialization of expensive computations or data fetches.
3. Enhance User Experience: Provides a seamless interaction experience without losing data or context.

Basic Syntax

Wrap dynamic components with <KeepAlive>:

<keep-alive>
  <component :is="currentView"></component>
</keep-alive>

Example 1: Caching Views

Template:

<template>
  <div>
    <keep-alive>
      <component :is="currentView"></component>
    </keep-alive>
    <button @click="currentView = 'ViewA'">Switch to View A</button>
    <button @click="currentView = 'ViewB'">Switch to View B</button>
  </div>
</template>

Script:

<script>
import ViewA from './ViewA.vue';
import ViewB from './ViewB.vue';

export default {
  data() {
    return {
      currentView: 'ViewA'
    };
  },
  components: {
    ViewA,
    ViewB
  }
};
</script>

Explanation:

• State Preservation: Switching between ViewA and ViewB retains each view’s state.
• Cached Components: Components wrapped in <KeepAlive> remain in memory until the app is destroyed.

Example 2: Excluding and Including Components

You can control which components are cached using the include and exclude props with regular expressions, strings, or arrays.

Template:

<keep-alive include="ViewA" exclude="ViewC">
  <component :is="currentView"></component>
</keep-alive>

Key Points:

• include="ViewA": Only ViewA will be cached.
• exclude="ViewC": ViewC will not be cached even if it appears.

Example 3: Lifecycle Hooks with <KeepAlive>

When using <KeepAlive>, components can access specific lifecycle hooks:

1. activated: Triggered when the component is re-displayed.
2. deactivated: Triggered when the component is hidden but not destroyed.

Template:

<template>
  <keep-alive>
    <component :is="currentView"></component>
  </keep-alive>
  <button @click="currentView = 'ViewA'">Switch to View A</button>
  <button @click="currentView = 'ViewB'">Switch to View B</button>
</template>

Script:

<script>
export default {
  data() {
    return {
      currentView: 'ViewA'
    };
  },
  components: {
    ViewA: {
      template: '<div>View A</div>',
      activated() {
        console.log('View A Activated');
      },
      deactivated() {
        console.log('View A Deactivated');
      }
    },
    ViewB: {
      template: '<div>View B</div>'
    }
  }
};
</script>

Explanation:

• Activated Hook: Executes logic when the component becomes visible again.
• Deactivated Hook: Executes cleanup or pause logic when the component is hidden.

When Not to Use <KeepAlive>

• Heavy Caching: Avoid caching too many components, as it may lead to high memory usage.
• Frequent State Changes: Components with rapidly changing states might not benefit from caching.
• One-Time Views: If a view is unlikely to be revisited, caching it might be unnecessary.

Best Practices

1. Selective Caching: Use include and exclude to cache only necessary components.
2. Efficient Lifecycle Hooks: Leverage activated and deactivated for optimized state management.
3. Limit Scope: Avoid wrapping the entire application with <KeepAlive>.

Conclusion

The <KeepAlive> component is an essential tool for optimizing performance and enhancing the user experience in Vue applications. By intelligently caching components, you can preserve state, improve load times, and create seamless interactions.

For more advanced Vue tutorials, visit The Coding College.