beforeCreate：組件實(shí)例初始化時(shí)調(diào)用，此時(shí)數(shù)據(jù)和事件未設(shè)置，無(wú)法訪問(wèn)this.$data和this.$el；2. created：實(shí)例創(chuàng)建完成後調(diào)用，數(shù)據(jù)、方法已初始化，但DOM未掛載，適合進(jìn)行數(shù)據(jù)初始化和API調(diào)用；3. beforeMount：掛載前調(diào)用，模板已編譯但未渲染到DOM，較少使用；4. mounted：組件掛載完成後調(diào)用，this.$el可用，常用於DOM操作、初始化第三方庫(kù)或數(shù)據(jù)獲??；5. beforeUpdate：數(shù)據(jù)更新時(shí)、重新渲染前調(diào)用，可訪問(wèn)更新前的DOM狀態(tài)；6. updated：組件更新後調(diào)用，DOM已重新渲染，適合執(zhí)行更新後的DOM操作，需避免無(wú)保護(hù)的狀態(tài)修改以防循環(huán)觸發(fā)；7. beforeUnmount（Vue 3）/beforeDestroy（Vue 2）：組件卸載前調(diào)用，實(shí)例仍可用，應(yīng)在此清理事件監(jiān)聽(tīng)器、定時(shí)器、訂閱等；8. unmounted（Vue 3）/destroyed（Vue 2）：組件卸載後調(diào)用，所有綁定和子組件已被移除，可用於最終清理或日誌記錄；此外還有errorCaptured用於捕獲子組件錯(cuò)誤，renderTracked和renderTriggered（Vue 3）用於調(diào)試響應(yīng)式依賴；生命週期順序?yàn)椋篵eforeCreate → created → beforeMount → mounted → beforeUpdate → updated → beforeUnmount → unmounted，Composition API中使用onMounted、onUpdated等函數(shù)，執(zhí)行順序不變；最佳實(shí)踐建議儘早獲取數(shù)據(jù)，created比mounted更適合發(fā)起請(qǐng)求，尤其在服務(wù)端渲染場(chǎng)景中。

In Vue.js, lifecycle hooks are special methods that allow you to run code at specific stages of a component's life — from creation to destruction. Understanding their order is crucial for tasks like data fetching, DOM manipulation, or cleanup.

Here are the main lifecycle hooks in a Vue component (using Options API), listed in the order they are called:

1. beforeCreate

• Called right when the component instance is initialized.
• At this point, data observation, events, and reactive properties have not been set up yet.
• this.$data and this.$el are not accessible.

Use case: Rarely used, but can be helpful for debugging initialization issues.

2. created

• Called after the instance is created.
• Data, methods, computed properties, and watchers are now set up.
• However, the component's DOM element ( $el ) is not yet created , so you can't access the template or mount point.

Use case: Ideal for initial data setup, starting API calls, or setting up event listeners.

3. beforeMount

• Runs right before the component is about to be mounted (rendered into the DOM).
• The template has been compiled, but no DOM rendering has happened yet.

Use case: Not commonly used, but can be useful for final checks before rendering.

4. mounted

• Called after the component has been mounted and the DOM is rendered.
• this.$el is now available and can be accessed.
• If the component has child components, they may not all be mounted yet.

Use case: Commonly used for:

• Fetching initial data (though sometimes better in created )
• Working with DOM elements (eg, initializing 3rd-party libraries)
• Setting up timers or subscriptions

5. beforeUpdate

• Called when reactive data changes, before the virtual DOM is re-rendered and patched.
• You can access the old DOM state here.

Use case: Useful for caching data or performing logic before an update.

6. updated

• Called after the component's DOM has been re-rendered due to data changes.
• Virtual DOM has been re-rendered and patched.

Use case: Perform DOM operations after an update. Be cautious — avoid modifying state here unless guarded, to prevent infinite loops.

7. beforeUnmount (Vue 3) / beforeDestroy (Vue 2)

• Called right before the component is destroyed.
• The instance is still fully functional.
• Cleanup tasks should be done here.

Use case: Essential for cleaning up:

• Event listeners
• Timers ( setInterval , setTimeout )
• Subscriptions or WebSocket connections
• Third-party integrations

8. unmounted (Vue 3) / destroyed (Vue 2)

• Called after the component has been removed from the DOM and all its bindings are unbound.
• All child components are also destroyed.

Use case: Final cleanup or logging; component instance is no longer usable.

Optional: Error Handling Hooks

• errorCaptured : Called when an error from a descendant component is captured.
• renderTracked / renderTriggered (Vue 3): Debugging hooks for tracking reactivity during rendering.

Summary of Execution Order:

 beforeCreate
 → created
 → beforeMount
 → mounted
 → beforeUpdate
 → updated
 → beforeUnmount // beforeDestroy in Vue 2
 → unmounted // destroyed in Vue 2

?? Note: In Vue 3 Composition API , you use onMounted() , onUpdated() , etc., inside setup() , but the underlying lifecycle sequence remains the same.

Quick Tip:
Don't fetch data in mounted if you can do it earlier — created is often better to start loading data as soon as possible, especially in SSR (Server-Side Rendering) contexts.

Basically, just follow the flow: setup → render → update → cleanup.

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