The relationship between the v-on event binding function and the methods function in the Vue document

In the Vue framework, the v-on directive is used to bind DOM events to methods of Vue instances. This allows Vue applications to combine interactivity with data responsiveness, allowing the user interface to dynamically change based on user input and actions.

However, there is no detailed description of the relationship between the v-on event binding function and the methods function in the Vue document. This has brought some confusion to novice developers. This article will discuss this issue in detail.

First of all, we need to understand the syntax of v-on, which can receive a parameter, which is the name of the event to be bound, such as click, keyup, mouseover, etc. Next is the JavaScript expression or method name to be executed. However, in the Vue documentation, we often see that the event binding function of v-on is defined as a method name, and this method name is not declared in the Vue instance, but is declared under the methods attribute.

In fact, the Vue framework allows event binding functions to be written as methods methods of the Vue instance, which means that all methods declared in the Vue instance can be used as v-on event binding functions. For example, in the following code, we can see that v-on's event binding function calls a method in the Vue instance:

<template>
  <button v-on:click="increment">增加</button>
</template>

<script>
  export default {
    data() {
      return {
        count: 0
      };
    },
    methods: {
      increment() {
        this.count++;
      }
    }
  };
</script>

In the above code, we define a data attribute count, and then Declare the increment method in methods. When the button is clicked, the increment method is called, executing the count statement to update the data from the Vue data reactive system. The increment method here is used as the event binding function of the v-on instruction, which is a classic event binding method.

However, there is a more concise event binding method in Vue, which does not use the methods attribute, but directly writes the Vue instance method as an expression. For example, the following code will achieve the same function as the above example:

<template>
  <button v-on:click="count++">增加</button>
</template>

<script>
  export default {
    data() {
      return {
        count: 0
      };
    }
  };
</script>

As you can see, in this case, we do not need to add the increment method in the methods attribute, but directly in the v-on event Write the JavaScript expression count in the bound function parameter. Vue will automatically convert the expression into a function and bind it to the event.

But it should be noted that this event binding method is only suitable for simple logic. If more complex logic is involved or reuse is required, it is recommended to define the event binding function as methods.

To sum up, the v-on directive in Vue can bind DOM events to methods of Vue instances. Event binding functions can be defined as methods or JavaScript expressions on the Vue instance, depending on the complexity and reusability required for event binding. I hope this article can help developers better understand the relationship between the v-on event binding function and the methods function.

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