Detailed explanation of v-model function in Vue3: application of two-way data binding

With the continuous development of front-end technology, Vue, as a popular front-end framework, is also constantly updated and iterated. The latest version, Vue3, introduces many new features, making it more convenient and flexible to use.

Among them, the v-model function is one of the new features worth mentioning in Vue3. It can achieve two-way data binding, that is to say, when using the v-model function, it can not only easily realize communication between parent and child components, but also automatically bind the data entered by the user with the data in the component. Next, this article will provide a detailed explanation of the v-model function in Vue3 and explore its use in practical applications.

1. Basic usage of v-model function

In Vue3, the basic usage of v-model function does not change much from that in Vue2. For an ordinary input tag, we can use the v-model function in the tag to implement two-way data binding.

For example, in the following code:

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

<script>
export default {
  data() {
    return {
      message: "",
    };
  },
};
</script>

We first define a data named message in data. Then we use the v-model function in the input tag to two-way bind the data entered by the user to the data. In this way, when the user enters data in the input box, the data will be automatically synchronized to the message in data. When we use message, we can also render it directly to the interface.

2. v-model function in custom components

In some cases, we need to use custom components and apply v-model to these components. In Vue3, we can implement the v-model function in a custom component by adding the model option to the component.

For example, in the following code:

<template>
  <div>
    <my-input v-model="message"></my-input>
  </div>
</template>

<script>
import MyInput from "./MyInput.vue";

export default {
  components: {
    MyInput,
  },
  data() {
    return {
      message: "",
    };
  },
};
</script>

We use a custom component my-input in the template and bind it to the message in data. Then in the custom component, we need to add a model option:

<template>
  <input :value="value" @input="$emit('update:value', $event.target.value)" />
</template>

<script>
export default {
  props: ["value"],
};
</script>

In the custom component, we specify value as the props of the component and pass the value entered by the user through $emit('update:value ', $event.target.value) event is updated to value. If we use the v-model function to bind a custom component, Vue will automatically pass the value of $vnode.model into the component as a prop, and will combine the value of $emit('update:propName', value) with $ The vnode.model.sync property is bound. Next, we will show you how to use the v-model function in a custom component.

<template>
  <div>
    <my-input v-model="message"></my-input>
  </div>
</template>

<script>
import MyInput from "./MyInput.vue";

export default {
  components: {
    MyInput,
  },
  data() {
    return {
      message: "",
    };
  },
};
</script>

In the MyInput component, we add a model option to update the value to value. The value of this value will be received from the parent component when the component is initialized, and updated as user input changes.

When we use v-model in the parent component to bind the custom component, Vue will automatically generate code to bind the component to the data of the parent component.

<my-component v-model="foo"></my-component>

After doing this, we can not only easily read and operate the custom component in the parent component, but also achieve two-way binding of data.

3. Application of v-model in forms

Forms are a very important part of our front-end development. In Vue3, the v-model function also provides a very convenient implementation method. We can use the v-model function to automatically bind the data in the form to the state of the component, thereby achieving very convenient and efficient form operations.

For example, in the following code:

<template>
  <div>
    <form>
      <label>名字：</label>
      <input v-model="name" />
      <br />
      <label>年龄：</label>
      <input v-model="age" />
    </form>

    <div>
      <h3 id="您的名字是-name">您的名字是：{{ name }}</h3>
      <h3 id="您的年龄是-age">您的年龄是：{{ age }}</h3>
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      name: "",
      age: "",
    };
  },
};
</script>

We can see that in this code, we use the v-model function to bind the input tag in the form. When the user successfully enters data in the input box, Vue3 will automatically save the data to the state of the component and update it. And when we display the component status in the interface through double bracket binding, we can directly read the data saved in v-model.

In short, in Vue3, the v-model function can not only realize two-way data binding between parent and child components, but also conveniently bind the data in the form to the state of the component, thereby achieving fast , efficient and convenient operation. Therefore, using the v-model function in Vue3 can allow us to develop front-end projects more efficiently and improve our application level in front-end development.

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