The setup function in Vue3: the core component configuration method of Vue3

With the continuous advancement and change of front-end technology, more and more developers are beginning to use Vue.js as an important tool for front-end development. In the latest version of Vue.js, Vue3, the setup function has become the core component configuration method of Vue3.

What is the setup function of Vue3?

In Vue3, each component has a setup function. The setup function is a life cycle function in Vue3. Its function is to initialize the component. The setup function is called before the beforeCreate function, which replaces the data, computed, methods and other options in Vue2 in some aspects.

What are the advantages of the setup function?

Using Vue3's setup function has the following advantages:

1. Explicit, simple code: Vue3 has strengthened its support for the functional programming paradigm. The setup function is a pure Javascript function. Vue3 hopes to expose as few internal details of Vue to developers as possible. Therefore, in the setup function, you can use ES6 syntax to write code more conveniently.
2. Better type inference: The setup function provides better type inference. Since the setup function is called before the component is initialized, Vue3 can more accurately type-check the component, which can optimize our code more efficiently.
3. Better responsive data: In Vue2, to make a certain data responsive, you need to add this attribute to data, or define it directly in the component. However, in Vue3, you can use the ref function in the setup function to create a reactive data.

How to use Vue3’s setup function?

First, we need to use the createApp function to create a Vue instance:

const app = Vue.createApp({
  // ...
})

Next, we define a setup function inside the component and pass the required parameters into this function:

const component = {
  props: {
    title: String,
    content: String
  },
  setup(props) {
    // ...
  }
}

The most important thing in the setup function is the return value, which returns an object that contains the data, methods, etc. used in the component. For example:

setup(props) {
  const title = Vue.ref(props.title)
  const content = Vue.ref(props.content)

  const setTitle = (newTitle) => {
    title.value = newTitle
  }

  const setContent = (newContent) => {
    content.value = newContent
  }

  return {
    title,
    content,
    setTitle,
    setContent
  }
}

In this example, we created two responsive data title and content through the ref function. We also defined two methods setTitle and setContent in the setup function and returned them to the component. .

Summary

The setup function in Vue3 is the core component configuration method of Vue3. It has the advantages of explicit, minimalist code, better type inference and better responsive data. What needs to be noted when using the setup function is that the return value must be an object, and the data, methods, etc. in the object need to be processed responsively using the ref function and the reactive function. Finally, I hope this article can help beginners better understand how to use the setup function in Vue3.

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