Keep-alive for caching components in Vue - Step-by-Step Execution

Concept Flow - Keep-alive for caching components

Component A Rendered

↓

Switch to Component B

↓

Component A Cached

↓

Component B Rendered

↓

Switch back to Component A

↓

Component A Restored from Cache

↓

Component B Cached

When switching components inside <keep-alive>, Vue caches inactive components instead of destroying them, so switching back restores their state instantly.

Execution Sample

Vue

<template>
  <keep-alive>
    <component :is="currentComponent" />
  </keep-alive>
</template>

<script setup>
import { ref } from 'vue'
const currentComponent = ref('CompA')
</script>

This code switches between components inside <keep-alive>, caching inactive ones to preserve their state.

Execution Table

Step	Action	Current Component	Cache State	Rendered Output
1	Initial render	CompA	Cache empty	CompA content shown
2	Switch to CompB	CompB	CompA cached	CompB content shown
3	Switch back to CompA	CompA	CompB cached	CompA restored from cache
4	Switch to CompB again	CompB	CompA cached	CompB restored from cache
5	End of demo	CompB	CompA cached	CompB content shown

💡 Demo ends after switching components and caching states.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
currentComponent	CompA	CompA	CompB	CompA	CompB	CompB
cache	empty	empty	CompA cached	CompB cached	CompA cached	CompA cached

Key Moments - 2 Insights

Why does switching back to CompA show its previous state instead of resetting?

Because <keep-alive> caches CompA when switching away (see Step 2), so when switching back (Step 3), Vue restores it from cache instead of recreating.

What happens to the component not currently shown?

It is kept in cache by <keep-alive> (see Cache State column), so it is not destroyed but stored for quick restoration.

Visual Quiz - 3 Questions

Look at the execution table at Step 2. What is the cache state after switching to CompB?

A Cache empty

B CompB cached

C CompA cached

D Both CompA and CompB cached

💡 Hint

Check the 'Cache State' column at Step 2 in the execution table.

At which step does CompA get restored from cache?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Rendered Output' column for when CompA is restored.

If <keep-alive> was removed, what would happen when switching components?

A Components would still cache their state

B Components would be destroyed and recreated each switch

C Only the first component would render

D Vue would throw an error

💡 Hint

Think about what does as shown in the concept flow and execution table.

Concept Snapshot

<keep-alive> wraps dynamic components to cache inactive ones.
Switching components inside it preserves their state.
Cached components are not destroyed but hidden.
Restoring a cached component is instant.
Useful for tabs, wizards, or expensive components.

Full Transcript

This visual trace shows how Vue's <keep-alive> caches components. Initially, CompA renders and cache is empty. When switching to CompB, CompA is cached and CompB renders. Switching back restores CompA from cache instantly. The cache always holds the inactive component. This avoids destroying and recreating components, preserving their state and improving performance. Removing <keep-alive> would cause components to be destroyed on switch. This is useful for UI patterns like tabs where you want to keep user input or scroll position.