Let's talk about why Vue 3 uses the setup() function

In Vue 2, we usually use optional API to create components, that is, by declaring life cycle functions, data, events, etc. to implement the functions of components.

However, Vue 3 provides a new API method called functional API, the most critical part of which is the setup() function.

setup() The function is a new concept in Vue 3 and does not exist in Vue 2. It allows us to better organize component code and improve component performance. So, why does Vue 3 use the setup() function?

1. Simplified component options

In order to make the component functions in Vue2 clearer and easier to maintain, Vue 3 introduced the setup() function. setup()The purpose of the function is to put the core logic of the functional API in a function to make the component options more concise.

Compared with Vue 2's option API, the setup() function is more modular and easier to manage. It separates the logic of the component and hands it over to the function, allowing the function to be responsible for creating and managing data, calculations, various methods and life cycle hooks in the component tag, thereby simplifying the component's options. Especially for large components, functional APIs make it easier to organize component code.

2. Better type deduction

Another advantage is that the type judgment of the setup() function is more accurate. In Vue 2, when using the optional API, Vue will deduce the type of the component at runtime and perform the corresponding operations. But since Vue cannot correctly infer some types, we need to add detailed type annotations to the component to help Vue make inferences.

In Vue 3, due to the limitations of the functional API, Vue is better able to infer the type of components. This means we don't have to add tons of type annotations when writing components. This is very helpful for reducing the amount of code and improving code readability.

3. Better performance

Due to the way the setup() function is designed, the performance of Vue 3 has also been greatly improved. In Vue 2, some component logic may be executed repeatedly when the component is mounted. This will cause some unnecessary calculations and network requests, reducing component performance.

In Vue 3, since setup() will only be executed once when the component is first mounted, and all logic in this function is lazily evaluated, it can Dramatically improve component performance.

In addition, when the component is re-rendered, since setup() will only be executed once when it is mounted for the first time, there is no need to re-execute it, which further improves the performance of the component.

Summary

setup() The function is an important part of Vue 3 based on the functional API, making the component code easier to manage and organize. If your components are large and complex, a functional API can make the code more modular and easier to maintain.

In addition, since the setup() function can improve the performance of the component and reduce the amount of code, the functional API is very useful when faster rendering and less code are required. of.

Therefore, the setup() function in Vue 3 is very important for modern front-end development, especially for Vue developers, it is worth mastering.

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