When To Use Vm Or This In Vue Js

Vue.js is a popular JavaScript framework that provides developers with a powerful toolset for building dynamic and interactive web applications. One common question that often arises when working with Vue.js is when to use `$vm` or `this` within your code. In this article, we'll explore the differences between these two approaches and provide guidance on when to use each one.

To start, let's clarify what `$vm` and `this` refer to in the context of Vue.js. When you're working within a Vue component, `this` refers to the component instance itself. This means that you can access data, methods, and computed properties defined within the component using `this`. On the other hand, `$vm` is a reference to the Vue instance, which allows you to access global properties and methods defined at the root level of your Vue application.

The decision to use `$vm` or `this` largely depends on the scope of the data or method you are trying to access. If you need to access data or methods specific to the current component instance, you should use `this`. For example, if you want to update a piece of data defined within the component or call a method that is specific to the component, you would use `this`.

export default {
  data() {
    return {
      message: 'Hello, Vue!'
    };
  },
  methods: {
    updateMessage() {
      this.message = 'Hi there!';
    }
  }
};

In the example above, we are defining a component with a `message` data property and an `updateMessage` method. Inside the `updateMessage` method, we are using `this` to access the `message` data property defined within the component.

On the other hand, if you need to access global properties or methods defined at the root level of your Vue application, you would use `$vm`. For example, if you have defined a global method or property that you want to access from within a component, you would use `$vm`.

// main.js
import Vue from 'vue';

Vue.prototype.$myGlobalMethod = function() {
  console.log('This is a global method.');
};

// Any component
export default {
  created() {
    this.$vm.$myGlobalMethod();
  }
};

In this example, we have defined a global method `$myGlobalMethod` using `Vue.prototype` in the `main.js` file. Inside a Vue component, we can access this global method using `$vm`.

In conclusion, the choice between using `$vm` or `this` in Vue.js comes down to the scope of the data or methods you are working with. Use `this` to access component-specific data and methods, and use `$vm` to access global properties and methods defined at the root level of your Vue application. By understanding the differences between these two approaches, you can write more efficient and maintainable Vue.js code.