How to automatically execute vue

Vue is a very excellent JavaScript framework that provides a way to create highly interactive and dynamic web applications. In the actual application of Vue, there will be situations where certain codes need to be automatically executed. At this time, we need to understand how Vue executes automatically.

Automatic execution in Vue can be achieved in the following ways:

1. created() life cycle hook function

After the Vue instance is created , you can use the created() life cycle hook function to directly execute certain codes. The created() life cycle hook function will be called after the Vue instance is created, before data observation and event configuration. Here you can write some code that requires preprocessing, such as data initialization, event binding, etc.

For example:

new Vue({
  el: '#app',
  data: {
    message: 'Hello, Vue!'
  },
  created() {
    console.log('Vue实例创建完成。')
  } 
})

In this example, we will print out a message after the Vue instance is created.

2. mounted() life cycle hook function

If you need to automatically execute some code after the Vue instance is mounted on the DOM, you can use the mounted() life cycle Cycle hook function. The mounted() life cycle hook function will be called after the Vue instance is mounted on the DOM. Here you can write some code that needs to operate the DOM or perform asynchronous request data after the rendering is completed.

For example:

new Vue({
  el: '#app',
  data: {
    message: 'Hello, Vue!'
  },
  mounted() {
    console.log('Vue实例挂载完成。')
  } 
})

In this example, we will print out a message after the Vue instance is mounted to the DOM.

3. watch attribute

The watch attribute is provided in Vue, which can monitor changes in data in the Vue instance and automatically execute certain codes after the data changes. The watch attribute is an object, the key name of the object is the name of the data attribute that needs to be monitored, the key value is a function, and the parameters of the function are the new value and the old value.

For example:

new Vue({
  el: '#app',
  data: {
    message: 'Hello, Vue!'
  },
  watch: {
    message(newValue, oldValue) {
      console.log('数据发生了变化。')
    }
  } 
})

In this example, we will print out a message after the message data attribute changes.

4. computed attribute

The computed attribute in Vue can be used to calculate and obtain the data attribute value in the Vue instance, and automatically perform certain operations when the data attribute changes. . The computed attribute is an object, the key name of the object is the name of the attribute that needs to be calculated, the key value is a function, and the return value of the function is the calculation result.

For example:

new Vue({
  el: '#app',
  data: {
    message: 'Hello, Vue!'
  },
  computed: {
    reverseMessage() {
      return this.message.split('').reverse().join('')
    }
  } 
})

In this example, we calculate the inverted value of message through the computed attribute, and automatically update the calculation result when the message changes.

To sum up, there are many ways to automatically execute code in Vue, which can be selected and combined according to specific needs. These methods can help us simplify the code, improve the reusability and maintainability of the code, and allow us to build excellent web applications more efficiently.

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