Detailed explanation of hook functions in Vue documentation

With the wide application of Vue in front-end development, Vue related documentation has become more and more important. Among them, hook function (Lifecycle Hooks) is a common concept in Vue documentation. This article will introduce the hook functions in the Vue document in detail to help readers better understand the life cycle of Vue.

1. What is a hook function

In Vue, each component instance will have some specific behaviors when it is created, mounted, updated, destroyed, etc. These behaviors can be defined and executed through hook functions. Hook functions are functions that are triggered at specific life cycle stages and can be used to perform some specific logic.

Hook functions in Vue are divided into two categories: life cycle hook functions and custom event hook functions. Among them, the life cycle hook function is a function that is automatically called during the running of the Vue instance, while the custom event hook function is a function that is manually called by the developer when a specific event is triggered.

2. Life cycle hook function

Vue’s life cycle is divided into 8 stages, and each stage has a corresponding life cycle hook function. Each life cycle stage and its corresponding hook function will be introduced below.

1. beforeCreate

This hook function is called before the Vue instance is created. At this time, the component instance has not been initialized. Only the options object of the component instance can be accessed at this stage.

2. created

This hook function is called after the Vue instance is created. At this time, the component instance has been created but has not yet been mounted on the DOM. At this stage you can access the component instance's options object and data, but you cannot access the DOM yet.

3. beforeMount

This hook function is called before the component is mounted to the DOM. At this stage, the component instance has been initialized but has not yet been rendered on the page.

4. mounted

This hook function is called after the component is mounted to the DOM. At this stage, the component instance has been initialized and has been rendered to the page. DOM elements can be accessed at this stage.

5. beforeUpdate

is called before the data is updated, when the component has not been re-rendered.

6. updated

is called after the data is updated, when the component has been re-rendered. The updated DOM elements are accessible at this stage.

7. beforeDestroy

Call this hook function before the component is destroyed. At this stage the component instance is still available.

8. destroyed

This hook function is called after the component is destroyed. At this stage, the component instance and all its instructions and event listeners have been destroyed. There should no longer be access to the component instance or the component's DOM elements at this stage.

3. Custom event hook function

In addition to the above life cycle hook function, Vue also supports custom event hook function. Developers can use the $on() method to listen for custom events and the $emit() method to trigger custom events.

4. Summary

Hook function is a very important concept in Vue and is often used in the development of Vue. This article introduces the hook functions in the Vue document, including life cycle hook functions and custom event hook functions. By understanding these hook functions, developers can better understand the life cycle of Vue instances and thus better manage and maintain the code of Vue applications.

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