How to upgrade from vue 2 to vue 3

How to upgrade from vue 2 to vue 3

Vue.js is a popular JavaScript framework known for its simplicity and versatility. With the release of Vue 3, developers have access to even more features and improvements that can enhance their web applications. However, upgrading from Vue 2 to Vue 3 can be a daunting task, especially for those who are new to the framework or have complex projects.

This comprehensive guide aims to provide step-by-step instructions on how to upgrade from Vue 2 to Vue 3. It will cover the major changes and new features in Vue 3, discuss the differences between the two versions, and provide tips and best practices for a smooth transition. Whether you’re a seasoned Vue.js developer or just starting out, this guide will help you navigate the upgrade process and take full advantage of Vue 3’s capabilities.

The guide will start by introducing the key concepts and differences between Vue 2 and Vue 3. It will then walk you through the necessary steps to upgrade your existing Vue 2 project to Vue 3. This includes updating project dependencies, adapting your code to the new syntax and APIs, and dealing with any breaking changes that may arise. Along the way, you’ll learn about the new features in Vue 3, such as the Composition API, the new rendering engine, and the enhanced reactivity system.

Throughout the guide, you’ll find code examples and explanations to help you understand the changes and implement them in your own projects. Additionally, you’ll get insights into the benefits of upgrading to Vue 3, including improved performance, better TypeScript support, and increased productivity. By the end, you’ll have a solid understanding of the upgrade process and be ready to take advantage of the latest features in Vue 3.

Table of Contents

What is Vue.js?

Vue.js is a popular JavaScript framework for building user interfaces. It is often referred to as a progressive framework, as it can be incrementally adopted to existing projects without much hassle. Vue.js is designed to be simple and flexible, allowing developers to easily create web applications with smooth and reactive user interfaces.

Some key features of Vue.js:

  • Reactivity: Vue.js features a reactive data-binding system that ensures the DOM updates automatically when the underlying data changes. This allows for a more fluid and responsive user experience.
  • Component-based architecture: Vue.js encourages the use of reusable and self-contained components, making it easy to build large-scale applications. Components can be composed together to create a cohesive user interface.
  • Virtual DOM: Vue.js uses a virtual DOM to efficiently update the real DOM. This helps in optimizing performance, as only the parts of the interface that have changed are updated.
  • Template syntax: Vue.js provides a simple and intuitive template syntax that allows you to declaratively render data and handle user interactions. This makes it easy to understand and write the code.
  • Vue CLI: Vue.js comes with an official command-line tool called Vue CLI, which provides a pre-configured development environment and makes it easy to scaffold and build Vue.js projects.

Overall, Vue.js is a powerful and versatile framework for building modern web applications. It has a growing community and is widely adopted by developers due to its simplicity, performance, and flexibility.

Why Upgrade to Vue 3?

Vue.js has been one of the most popular JavaScript frameworks in recent years, offering developers the ability to build interactive and dynamic web applications with ease. With the release of Vue 3, the framework introduces several new features and improvements that make it an even more powerful and efficient tool for front-end development.

Here are some reasons why you should consider upgrading to Vue 3:

  1. Improved Performance: Vue 3 includes a re-written rendering mechanism, which is much faster compared to Vue 2. The new compiler and runtime have been optimized to reduce bundle size and enhance rendering speed, resulting in overall better performance of your applications.
  2. Composition API: Vue 3 introduces a new API called the Composition API, which provides a more flexible and composable way to organize your code. With the Composition API, you can group related code logic together, making it easier to maintain and reuse code across your application.
  3. Tree-Shaking Support: Vue 3 fully supports tree-shaking, which means that unused code can be eliminated during the build process. This allows for smaller bundle sizes and improved application loading times.
  4. Teleport: Vue 3 introduces a new feature called Teleport, which allows you to render a component’s template content at a different location in the DOM hierarchy. This can be useful for cases such as modals, tooltips, and popovers, where you need to render content outside of the current component’s scope.
  5. Fragments: Vue 3 introduces the ability to use fragments, which allow you to have multiple root elements in a component’s template. This eliminates the need for unnecessary wrapper elements and enhances the flexibility of your component structure.

Overall, upgrading to Vue 3 brings performance improvements, new features, and enhanced developer experience to your Vue.js applications. It allows you to build more efficient and powerful applications while enjoying the benefits of the latest advancements in the Vue ecosystem.

Step 1: Understanding the changes


Before diving into the upgrade process, it’s important to understand the key changes introduced in Vue 3. This will help you navigate the upgrade process more effectively and take advantage of the new features and improvements.

See also:  What is difference between vue 2 and vue 3

Composition API

One of the major changes in Vue 3 is the addition of the Composition API. This new API provides a more flexible and powerful way to organize and reuse code logic in Vue components. It introduces the concept of Vue composition functions, which are functions that can be used to define reactive data, computed properties, methods, and lifecycle hooks.

The Composition API allows you to group related code together, making it easier to understand and maintain. It also promotes a more modular approach to building Vue components, as logic can be encapsulated in separate functions and reused across multiple components more easily.


Vue 3 has also made some changes to its reactivity system. The new reactivity system in Vue 3 provides better performance and a more fine-grained control over reactivity. This means that you can have more control over which parts of your component should be reactive, improving overall performance.

Vue 3 introduces a new reactive function, which can be used to create reactive objects and properties. The reactivity system now also handles reactive arrays and maps more efficiently.

Component Changes

Vue 3 has made several changes to the way components are used and defined. Some of the key changes include:

  • Fragment Syntax: In Vue 3, you can now use the fragment syntax to render multiple root elements without the need for a wrapper element.
  • Component Emit: The new component emit feature provides a more explicit way for child components to emit events to their parent components.
  • Async Components: Vue 3 introduces a new way to define asynchronous components using the defineAsyncComponent function.
  • Teleport: The new teleport feature allows you to render a component’s DOM content at a different location in the DOM tree.

Breaking Changes

Lastly, it’s important to be aware of any breaking changes introduced in Vue 3. Some of the changes may require modifications to your existing Vue 2 codebase in order to upgrade successfully. The Vue team has provided detailed documentation on the breaking changes, so make sure to review them before starting the upgrade process.

Understanding these changes will help you plan your upgrade strategy and ensure a smooth transition from Vue 2 to Vue 3.

Breaking Changes

Introduce the Composition API

The most significant change in Vue 3 is the introduction of the Composition API. The Composition API allows developers to organize their component logic in a more flexible and reusable way. Instead of relying solely on Options API, developers can now use Composition API to create components with composition functions and hooks.

With the Composition API, developers can:

  • Create reusable compositions
  • Compose and encapsulate component logic
  • Use reactive state and computed properties
  • Create custom hooks for sharing logic

New Template Syntax

Vue 3 introduces several changes to the template syntax:

  • Attribute binding syntax has been modified. Instead of using colon (:) for binding, you can now use the “v-bind:” prefix.
  • The “v-bind” directive now supports shorthand syntax. For example, instead of writing “

    “, you can now write “


  • The “v-if” and “v-for” directives now have priority over other directives, allowing for better composition and avoiding conflicts.
  • The “v-bind:key” directive is now required when using “v-for” with a component, instead of automatically inferring the key from the component instance.

Changes to Reactivity System

Vue 3 introduces changes to the reactivity system:

  • Reactivity is now deeply integrated into the core of Vue, allowing the reactivity system to be used outside of components.
  • Reactivity now uses Proxy instead of defineProperty, which allows Vue to better track reactivity and improves performance.
  • The “Vue.set” and “Vue.delete” methods have been removed. Developers should use the native JavaScript assignment and deletion syntax instead.

Updates to Fragments and Teleport

Updates to Fragments and Teleport

In Vue 3, the concept of fragments has been introduced, allowing multiple root elements in a component. Fragments are denoted by a special “