Vue 3: How to understand the vue 3 Composition API: setup()

The Composition API is a new way to organize and reuse logic in Vue 3 components. It provides more flexibility and modularity than the Options API, which was used in Vue 2. The setup() function is the entry point to using the Composition API. It is called before the component is mounted and allows you to define reactive state, computed properties, and methods.

The setup() function takes two arguments: props and context. Props are the properties that are passed to the component, while context provides access to the component instance, its properties, and lifecycle hooks.

Inside the setup() function, you can use the reactive() function to create reactive data objects, computed() function to define computed properties, and ref() function to define a reactive reference. Additionally, you can define methods and access the props and context objects.

The setup() function returns an object that contains the reactive data objects, computed properties, methods, and any other objects you want to expose to the component template.

Overall, the Composition API and setup() function in Vue 3 provide a more modular and flexible approach to organizing and reusing logic in components, making it easier to build complex applications.