Why is the initial value in vue in data?

Vue is a popular JavaScript framework that makes it easier for developers to interact with pages and provides a simple way to manage and update data in pages. In Vue, the initial value is usually stored in the component's data property. So why should the initial value be stored in data? This article will delve into this issue.

First, let's take a look at the basic structure of the Vue component. A Vue component usually contains three parts: template, script and style. Among them, the template describes the appearance and interaction mode of the component; the script contains the component's data, methods, life cycle hooks, etc.; the style is the component's style sheet.

In Vue, the initial value of the component is usually placed in the data attribute of the script part. For example:

Vue.component('my-component', {
  data: function() {
    return {
      message: 'Hello, Vue!'
    }
  }
})

In the above code, we define a Vue component named "my-component" and define a message in its data attribute with an initial value of "Hello, Vue!" Attributes. In this way, we can use the message attribute in the template:

<template>
  <div>{{ message }}</div>
</template>

In the above code, the interpolation expression {{}} is used to display the value of the message attribute.

So why put the initial value in data? There are mainly the following reasons:

1. Vue’s responsive system needs to monitor data changes of components. Only attributes in the data attribute will be monitored, so the initial value must be placed in data.
2. The data in the data attribute can be accessed by other parts of the component, including templates and methods. If the initial value is not in data, then it cannot be accessed from other parts of the component.
3. Saving data centrally in the data attribute helps organize and manage component data. In a large component, there may be multiple properties. Saving them all in data can be easily managed and maintained.
4. Vue’s developer documentation recommends saving the initial value in the data attribute, which is a best practice.

Therefore, although the initial value does not have to be saved in data in Vue, it is a best practice that helps organize and maintain the data of the component and is in line with Vue's design philosophy. and responsive system requirements.

Finally, one thing to note is that in Vue 3, the data attribute has been abandoned, and the setup function is used to manage the component's data. In the setup function, we can define a return object to store the component's data and methods. This not only meets the needs of a responsive system, but also makes the code more concise and easier to maintain.

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