在Vue 3 的Composition API 中，ref 用於管理基本類型或需要保持可變引用的響應(yīng)式狀態(tài)，並通過.value 訪問；reactive 更適合用於組合多個(gè)響應(yīng)式屬性的對(duì)象，且無需.value。 1. ref 支持重新賦值並保持響應(yīng)性，reactive 則在重新賦值後失去響應(yīng)性。 2. 在模板中使用時(shí)，ref 可自動(dòng)解包，而reactive 解構(gòu)後會(huì)失去響應(yīng)性，需配合toRefs 使用。 3. 性能方面，reactive 對(duì)複雜對(duì)象更高效，但通常差異不大。根據(jù)需求選擇即可。

When working with Vue's Composition API, especially in Vue 3, you'll often come across ref and reactive for managing reactive state. While they both help track changes and update the UI accordingly, they're not interchangeable — each has its own use case and behavior.

Here's how they differ and when to choose one over the other.

1. Basic Usage and Value Types

• ref is best for:
  • Primitive values ( string , number , boolean )
  • When you need to keep a reference to a value that might change
  • Keeping reactivity across function boundaries or loops

You access and modify it using .value :

 const count = ref(0)
count.value

• reactive works well for:
  • Objects (including arrays and nested objects)
  • Grouping related reactive data together in a single object

You use it directly without .value :

 const state = reactive({ count: 0 })
state.count

The main takeaway here is:
Use ref when dealing with primitives or needing a mutable reference. Use reactive when grouping multiple reactive properties into an object.

2. Reassignment Behavior Matters

This is a subtle but important difference.

If you have a ref , you can safely reassign it to another value and still retain reactivity:

 let count = ref(0)
count = ref(10) // Still reactive

But with reactive , if you reassign the variable, it loses reactivity:

 let state = reactive({ count: 0 })
state = reactive({ count: 10 }) // Reactivity lost on the new assignment

So, if you plan to completely replace the value later, ref is safer.

3. Template Usage and Destructuring Gotchas

In templates, ref automatically unwraps, so you don't need .value . That makes them convenient:

 <template>
  <div>{{ count }}</div>
</template>

<script setup>
const count = ref(5)
</script>

But if you destructure a reactive object, the destructured variables lose reactivity:

 const state = reactive({ count: 0, name: 'Vue' })
const { count } = state // ? Not reactive anymore

To fix this, you'd need to use toRefs :

 const state = reactive({ count: 0, name: 'Vue' })
const { count } = toRefs(state) // ? Now count is a ref

So, if you're planning to destructure your state, ref or toRefs are better choices.

4. Performance Considerations (Slight Edge)

Under the hood, reactive uses Proxy , while ref wraps the value in an object with a .value property. This means reactive may be slightly more performant for large, complex objects since it doesn't require wrapping every property in a ref.

However, unless you're dealing with very large datasets or performance-critical code, the difference is negligible.

So which should you use?

• Prefer ref for primitives and when flexibility with reassignment matters.
• Go with reactive when grouping related state into an object and you don't need to destructure.

They both do similar jobs but behave differently in edge cases.

基本上就這些。

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