Introduction to Composition API in Vue3

        In Vue 3, the Composition API is introduced, which is a new combined function API used to organize and reuse component logic more flexibly. Compared with the Options API in Vue 2, the Composition API provides better composability and code reusability. The following is an introduction and usage of the Composition API in Vue 3:

1. Introducing the Composition API: In Vue 3, you can use the setup() function to introduce the Composition API. The setup() function is a special function that is executed before the component is created. It receives two parameters: props and context. You can use the Composition API in the setup() function to organize the logic of the component.

2. Composition function: Composition API implements logic combination and reuse through a series of composition functions. These combination functions include ref, reactive, computed, watch, etc. The following is an introduction to some commonly used combination functions:

   • ref: used to create a responsive data reference. The referenced value can be accessed and modified via.value.

   • reactive: Used to create a responsive object. Reactive updates can be triggered by accessing and modifying an object's properties.

   • computed: Used to create a computed property. A value can be calculated dynamically based on changes in other reactive data.

   • watch: Used to monitor changes in a responsive data and execute the corresponding callback function.

3. Logical organization of components: Using the Composition API, you can organize the logic of components according to functions instead of options. You can put related reactive data, calculated properties, methods, etc. together to make the logic of the component clearer and maintainable.

4. life cycle hook: In Vue 3, the life cycle hook function is replaced by onBeforeMount, onMounted, onBeforeUpdate , onUpdated, onBeforeUnmount, onUnmounted and other functions. You can use these functions insetup()functions to perform corresponding life cycle operations. For more reference:Life cycle function in vue3-CSDN blog

5. Custom combination functions: In addition to using the built-in combination functions, you can also customize combination functions to achieve more complex logic reuse. Custom composition functions can receive parameters and return an object containing reactive data and methods.

        ​ ​ ​Using the Composition API can make the logic of the component clearer, maintainable and testable. It provides a more flexible way to organize and reuse component logic, making the code more readable and extensible. When using the Composition API, you can refer to the detailed introduction and sample code of the Composition API in the Vue 3 official documentation.