How to use life cycle functions to achieve code reuse and optimization in Vue

Vue is a popular JavaScript framework, and one of its features is the life cycle function. Lifecycle functions are an extension of Vue components, which provide the ability to call different methods at different stages of the component. By using life cycle functions, we can optimize the performance of Vue applications and achieve code reuse. This article will introduce the commonly used life cycle functions in Vue and provide practices on how to use these functions for code reuse and optimization.

1. Creation Phase

The Vue component will go through the creation phase when it is created. At this stage, Vue will call the beforeCreate and created life cycle functions in sequence.

1.1 beforeCreate

The beforeCreate function will be called when the component instance is created. This function is called before data and event listeners have been set. Therefore, the data and methods in the instance cannot be accessed at this stage. Typically, at this stage we initialize some component-level configuration. For example, a component can be configured by calling the global configuration object.

1.2 created

The created function will be called after the component instance is created. This function is called after the data and event listeners have been set up. Therefore, at this stage we have access to the instance's data and methods. At this stage we can perform some asynchronous operations in the component, such as obtaining data through axios or calling back-end services.

2. Mounting Phase

The next phase of the Vue component is the mounting phase. At this stage, Vue will call the beforeMount and mounted life cycle functions in sequence.

2.1 beforeMount

The beforeMount function is called before the component is mounted to the DOM. This function can be accessed immediately after the $data and $el properties of the instance are created. Therefore, at this stage we can perform some DOM related operations in the component.

2.2 mounted

The mounted function is called after the component is mounted to the DOM. This function is called after all elements in the component's template are mounted to the page. At this stage, we can obtain the width, height, distance and other information of the element and perform some position-related calculations on the component. In addition, we can also use the mounted function to create Vue instances of some components to implement recursive calling of sub-components and other scenarios.

3. Update Phase

The next phase of Vue components is the update phase. At this stage, Vue will call the beforeUpdate and updated life cycle functions in sequence.

3.1 beforeUpdate

The beforeUpdate function is called when the data attribute of the component changes, but the nodes in the virtual DOM have not been updated at this time. At this stage, we can obtain the data and status before the change and perform some comparisons and calculations to decide whether to update the component's DOM.

3.2 updated

The updated function is called after the component's DOM is updated. At this time, the nodes in the virtual DOM have been updated. At this stage, we can manipulate the updated DOM, such as adding styles to elements or performing some calculations and operations through the DOM API.

4. Destruction Phase

When the Vue component is no longer needed, it will be destroyed. Before destruction, Vue will call the beforeDestroy and destroyed life cycle functions in sequence.

4.1 beforeDestroy

The beforeDestroy function is called before the component is destroyed, when the component instance is still available. At this stage, we can clean up the binding relationship between the component and the external library, cancel the timer, clear the event listener, etc.

4.2 destroyed

The destroyed function is called after the component is destroyed. At this stage, the component instance, the DOM node and its event listeners, and all child components have been deleted. At this stage, we can clear the component's cache or perform some other cleanup operations.

To sum up, the life cycle function provides us with a very flexible way to manage the behavior of Vue components at different stages. By using life cycle functions correctly, we can achieve code reuse and optimization. For example, when reusing Vue component code, we can use the created lifecycle function to transfer data and make multiple calls between components. When optimizing component performance, we can use the lifecycle function to clear caches and release component resources.

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