Detailed explanation of Vue life cycle and description of common methods

Vue is a popular JavaScript framework for developing front-end applications. It provides expressive features that allow developers to easily build interactive web applications. The Vue life cycle is the stages that a Vue component goes through during runtime. These stages allow developers to execute some key code during the component life cycle. This article will introduce the Vue life cycle and its common methods in detail.

Vue Lifecycle

Vue provides 8 different lifecycle hooks that are called at different stages to enable developers to control and customize the behavior of Vue components. The eight hooks of the life cycle are as follows:

1. beforeCreate()
2. created()
3. beforeMount()
4. mounted()
5. beforeUpdate()
6. updated()
7. beforeDestroy()
8. destroyed()

Introduction to life cycle methods

1. beforeCreate()

This is the first life cycle before the Vue component is created. At this time, the data object and listening events of the Vue instance have not been initialized. At this stage, developers can register global directives, mixins, and filters.

2. created()

In this stage between beforeCreate and mounted, the data object and listening events of the Vue instance have been initialized. At this time, you can access the properties and methods on the instance, but the DOM and other subcomponents have not yet been mounted. At this stage, some asynchronous requests and other operations can be implemented.

3. beforeMount()

At this stage, the Vue instance checks the component template and prepares it for insertion into the DOM. At this stage, some operations to access DOM nodes can be implemented.

4. mounted()

At this time, the Vue instance inserts the component template into the DOM and completes compilation and rendering. At this time, the $data of the Vue instance has been proxied to the Vue instance itself, and the members in $data can be accessed through the instance. At this stage, some operations such as creating timers and building maps can be implemented.

5. beforeUpdate()

At this stage before the data is updated, the Vue instance has detected changes in the data, but has not yet started re-rendering. At this stage, some operations such as checking and changing the data before updating can be implemented.

6. updated()

At this time the Vue instance has been re-rendered and the DOM has also been updated. At this stage, you can compare the differences between the two renderings before and after, and perform some DOM operations.

7. beforeDestroy()

At this stage before the component is destroyed, the Vue instance is still fully available. At this stage, some cleaning operations can be implemented.

8. destroyed()

At this time the Vue instance has been completely destroyed, and all its instructions, computed properties, listeners and observers have been deleted. At this stage, some operations such as cleaning variables and canceling event binding can be implemented.

The life cycle is very important when developing applications with Vue. Understanding how each life cycle stage is called, and mastering the usage skills and methods of each stage, can greatly help us better understand the internal working principles of Vue applications, and write more efficient, reliable, and easier to maintain code.

Commonly used life cycle methods

1. watch

After the Vue component instance is created, you can use watch to monitor data changes (triggered by other components ) and respond to it. Watch will only monitor data changes and will not interfere with other Vue life cycles.

2. computed

Vue defines the computed attribute, which associates the state of the Vue component with the operation defined in the Vue instance. Using the computed property, Vue can dynamically update the results of computed properties when the component's state changes. The computed attribute is responsive and has a caching mechanism. When the component state does not change, it will return the result of the last calculation.

3. props

props is a method of passing information between components through properties. During component initialization, the Vue instance stores props into component properties so that data can be passed between components. When a component receives props, those props are also reactive, so the component can handle them accordingly.

Summary:

This article introduces the details of the Vue life cycle and its methods, including 8 different life cycle hooks and commonly used life cycle methods. In order to develop more efficient and reliable applications, developers need to understand the life cycle of a Vue instance and be familiar with how to operate at different stages. Now that you have a grasp of the Vue lifecycle, you can start writing better Vue applications.

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