The combination of v-model directive and calculated property function in Vue document

Vue.js is a modern, flexible JavaScript framework for building user-interactive web applications. This article will introduce the combined use of the v-model directive and calculated property functions in the Vue document.

The v-model directive is a built-in directive in Vue that is used to create two-way data binding on form elements. It makes it very easy to synchronize data into Vue's data model as the user enters data. For example, v-model can be bound to the data attribute of the Vue component as follows:

<template>
  <div>
    <input v-model="message" />
    <p>{{ message }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      message: ''
    }
  }
}
</script>

In the above example, when the user types text in the input box, Vue will automatically update the message's value, so the corresponding data binding displays the text entered by the user.

However, in some cases, some specific properties need to be calculated based on user input data and updated into Vue's data model. This can be achieved using computed property functions. The computed property function is a special Vue property that calculates and derives a new property based on the state of the Vue instance. Computed property functions automatically update when the properties they depend on change, so they can be used to handle logic in components.

When using the computed property function in conjunction with the v-model directive, you can convert user-input data into a computed property and update it to Vue's data model by setting the setter attribute in the computed property function. middle. For example, you can create the following computed property function:

<template>
  <div>
    <input v-model="fullName" />
    <p>First Name: {{ firstName }}</p>
    <p>Last Name: {{ lastName }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      fullName: ''
    }
  },
  computed: {
    firstName: {
      get() {
        return this.fullName.split(' ')[0]
      },
      set(value) {
        this.fullName = value + ' ' + this.lastName
      }
    },
    lastName: {
      get() {
        return this.fullName.split(' ')[1]
      },
      set(value) {
        this.fullName = this.firstName + ' ' + value
      }
    }
  }
}
</script>

In the above example, the v-model directive is bound to the fullName property, and the other two computed property functions calculate the first of the property and the second word (via the string's split method). Additionally, both computed properties have setter properties set so that the fullName property is updated when the user modifies its value. When the user enters text in the input box, Vue automatically updates the fullName property, and since the computed property function relies on it, the firstName and lastName properties are automatically updated.

In this way, derivation and updating of properties based on user input can be easily achieved using the v-model directive and computed property functions. This technique is useful whether you have a simple form containing text input fields and checkboxes or a dynamic form containing multiple input elements. However, we need to be aware that using too many computed property functions may affect the performance of the application. Therefore, when using this technique, you need to be aware of the complexity of the data model, as well as the number and complexity of the computed attribute functions.

In short, the v-model directive and calculated property function in the Vue document are two very useful functions. They help us implement forms and interactive components more easily, while also making the code more elegant and readable.

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