What is the difference between v-bind and v-model directives?

In Vue.js, v-bind and v-model are two commonly used directives, but they serve different purposes and operate with distinct mechanisms.

v-bind

The v-bind directive is primarily used to bind HTML attributes to data properties within the Vue instance. It is unidirectional, meaning that data changes update the view, but changes in the view do not directly affect the data. v-bind is particularly suitable for dynamically applying data to tag attributes, such as setting the src attribute of an image or applying CSS classes.

Example:

html
<template>
  <img v-bind:src="imageUrl">
</template>

<script>
export default {
  data() {
    return {
      imageUrl: 'path/to/image.jpg'
    }
  }
}
</script>

In this example, the src attribute of the image is bound to the imageUrl data property, and when the value of imageUrl changes, the image source updates accordingly.

v-model

The v-model directive establishes bidirectional data binding between form inputs and the application state. It not only passes data from the Vue instance to form input fields but also updates the data in the Vue instance when the field's content changes. This bidirectional binding simplifies handling form inputs significantly.

Example:

html
<template>
  <input v-model="username">
</template>

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

In this example, the input form element is bound to the username data property via v-model. As the user types into the input field, the username value updates in real-time, and vice versa.

Summary

Overall, v-bind is used for unidirectional binding, attaching data to element attributes. Conversely, v-model creates bidirectional data binding on form elements, streamlining data synchronization between the view and the model. While they share overlapping functionalities (such as binding data to attributes), their specific application contexts and data flow directions differ substantially.