How to use v-on:input to monitor input box input events in Vue

Vue is a popular JavaScript framework that makes web development more efficient and simpler. Among them, using v-on:input to monitor input box input events is a common requirement. This article will introduce in detail how to use v-on:input to monitor input box input events in Vue.

1. v-on:input command

The v-on:input command is a command in Vue used to monitor input events in the input box. It can monitor input, textarea, contenteditable and other elements. input event to achieve.

Using the v-on:input directive is very simple. You only need to bind the v-on:input attribute to the element that needs to be monitored, and then define the corresponding method in the Vue instance.

For example, in the following code, we define an input box and a div element that displays the input content. Use the v-on:input directive on the input element to bind a method that will be called when content is entered in the input box and update the input content to the message variable in data. In the div element, we use {{}} interpolation to render the message variable in the data.

<div id="app">
  <input v-on:input="updateMessage">
  <div>{{message}}</div>
</div>

<script>
  var app = new Vue({
    el: '#app',
    data: {
      message: ''
    },
    methods: {
      updateMessage: function (event) {
        this.message = event.target.value
      }
    }
  })
</script>

2. Use the v-model directive to simplify the code

Although the v-on:input directive can be used to monitor input events in the input box, in actual development, we usually use v-model directive to simplify the code.

The v-model directive is equivalent to binding a v-on:input directive and a value attribute at the same time. Therefore, we can implement the above example code by using the v-model directive on the input element.

<div id="app">
  <input v-model="message">
  <div>{{message}}</div>
</div>

<script>
  var app = new Vue({
    el: '#app',
    data: {
      message: ''
    }
  })
</script>

After using the v-model directive, you no longer need to define the updateMessage method in methods to update data. Vue will automatically update the value in the input box to the message variable in data.

3. Monitor other input events

In addition to input events, Vue also provides other input events to monitor, such as change, keyup, keydown, etc. We can pass the corresponding event name when using the v-on:input directive to specify the event to be monitored.

For example, in the following code, we listen to the change event of a textarea element, and the event will be triggered when the user completes input and leaves the element. In the Vue instance method, we determine whether the content entered by the user meets our requirements based on the value represented by event.target.value.

<div id="app">
  <textarea v-on:change="checkInput"></textarea>
</div>

<script>
  var app = new Vue({
    el: '#app',
    methods: {
      checkInput: function (event) {
        if (event.target.value === '') {
          alert('输入内容不能为空！')
        } else {
          alert('输入内容为：' + event.target.value)
        }
      }
    }
  })
</script>

4. Summary

Using the v-on:input directive in Vue can easily implement the function of monitoring input events in the input box. At the same time, we can also use the v-model directive to simplify the code. In addition to input events, Vue also provides a variety of input events for monitoring user input, which can be selected according to specific needs. Once you master these skills, I believe you will be able to complete Vue development work more efficiently.

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