How to migrate from Vue 2 to Vue 3

Migrating from Vue 2 to Vue 3: A Comprehensive Guide

Introduction

The Vue.js team has recently announced that Vue 2 will reach its end of life by 2023. This signifies the need for developers to consider migrating their Vue 2 applications to Vue 3. Despite the challenges associated with upgrading, the Vue.js team released a Migration Build in June 2021 to facilitate the migration process. In this article, we will share our experience of migrating a large-scale application from Vue 2 to Vue 3.

Should I Migrate to Vue 3?

Absolutely. With Vue 2.0 approaching its end of life, it’s crucial to plan the migration. Moreover, Vue 3 offers significant improvements, including:

1. Faster Rendering

Vue 3 benchmarks show that the initial render is up to 55% faster, updates are up to 133% faster, and memory usage has been reduced by 54%.

2. Improved TypeScript

Vue 3’s codebase is entirely written in TypeScript, providing auto-generated type definitions, type inference, and props type checking within templates.

3. Composition API

While the Composition API may seem unfamiliar initially, it enhances the Developer Experience once you become accustomed to it. However, the Options API, if preferred, is still fully supported.

Workflow Strategy

In our experience migrating a large-scale application, we executed the migration while simultaneously working on new features and bug fixes. To optimize this process, we followed a structured workflow strategy:

1. Parallel Work

• New features, product support, and tech debt were addressed in the Vue 2 application.
• Vue 3 migration work was conducted on a separate branch with multiple sub-branches.

2. Synchronization

• For every change pushed to the main branch, we synchronized the Vue 3 branch and made necessary adjustments for compatibility.

3. Regression Testing

Ensuring a successful migration meant not breaking anything. Therefore, we conducted a full regression test to ensure every feature worked as intended.

Migration Strategy

A complete migration involves the following six steps:

1. Install Vue’s Migration Build

The Vue Team introduced @vue/compat, known as the Migration Build, facilitating compatibility between Vue 2 and Vue 3 during the migration process.

Installation Steps:

• Upgrade tooling if applicable (e.g., custom Webpack setup or vue-cli).
• Modify package.json to install the necessary packages.

• Enable the Migration Build’s compatibility mode in your build system.

2. Fix Migration Build’s Errors

Although the Migration Build is set up, there might still be errors preventing the application from running smoothly. Common errors include changes in named and scoped slots, the deprecation of the functional attribute, modifications in the mounted container behavior, and adjustments needed for v-if combined with v-for.

3. Fix Migration Build’s Warnings

Even if the application runs with warnings, it’s essential to address them for a seamless transition. Common warnings include changes in app initialization, Vue Global API modifications, and adjustments for reactive property setters.

4. Fix Package Compatibilities

Vue packages, both official and unofficial, need to be upgraded to their Vue 3-compatible versions. This includes popular libraries like Vuex and Vue Router. Ensure compatibility with Vue 3 and address any breaking changes introduced in the packages.

5. Fix TypeScript Support

Adapt TypeScript declaration files for .vue files to work with Vue 3. Update module declarations to reflect the changes introduced in Vue 3.

6. Fully Switch to Vue 3

Once confident in the application’s stability and functionality, it’s time to eliminate the Migration Build. Uninstall the @vue/compat package, remove changes made to configuration files, and celebrate the successful migration.

Conclusion

While migrating from Vue 2 to Vue 3 may pose challenges, it is a necessary step to keep applications modern and supported. Our comprehensive guide provides insights into the migration process, from planning and strategy to addressing specific issues in each step. Embrace the changes, invest the time and effort required, and ensure a smooth transition to Vue 3 for a more efficient and future-proofed application. Happy coding!