Vue 3.0 ‘One Piece’ Released: Complete Overview

After over two years of development, Vue 3.0 “One Piece” has officially been released. This is the most significant update in Vue’s history, bringing fundamental improvements to the framework’s architecture, performance, and developer experience. As someone who has been following Vue since version 1.x, I’m excited to walk you through what makes this release so important.

The Composition API: A Paradigm Shift

The headline feature of Vue 3 is the Composition API. While the Options API that Vue 2 developers know and love is still fully supported, the Composition API offers a new way to organize component logic that scales better for complex applications.

The key insight behind the Composition API is that related logic should stay together. In the Options API, a single feature’s code is split across data, computed, methods, and lifecycle hooks. In the Composition API, all logic for a feature can be grouped in a single function that can be extracted and reused.

import { ref, computed, onMounted, watch } from 'vue'

// Composable function - reusable across components
export function useUserSearch(initialQuery = '') {
  const query = ref(initialQuery)
  const users = ref([])
  const isLoading = ref(false)
  const error = ref(null)
  
  const filteredUsers = computed(() => 
    users.value.filter(u => 
      u.name.toLowerCase().includes(query.value.toLowerCase())
    )
  )
  
  async function searchUsers() {
    isLoading.value = true
    error.value = null
    try {
      const response = await fetch(`/api/users?q=${query.value}`)
      users.value = await response.json()
    } catch (e) {
      error.value = e.message
    } finally {
      isLoading.value = false
    }
  }
  
  // Watch for query changes with debounce
  watch(query, () => {
    searchUsers()
  }, { debounce: 300 })
  
  onMounted(searchUsers)
  
  return { query, users, filteredUsers, isLoading, error, searchUsers }
}

Performance Improvements

Vue 3’s virtual DOM was rewritten from scratch with a focus on performance. The key improvements include:

• Compiler-informed Virtual DOM: The template compiler now generates optimized render functions that skip static content and cache dynamic nodes
• Tree-shaking Support: Unused features are eliminated at build time, resulting in smaller bundles. A minimal Vue 3 app can be under 10KB gzipped
• Proxy-based Reactivity: Using JavaScript Proxy instead of Object.defineProperty means better performance and the ability to detect property additions/deletions

In benchmarks, Vue 3 is roughly twice as fast as Vue 2 for updates and uses 50% less memory.

New Built-in Components

Vue 3 introduces three new built-in components that solve common patterns:

• Teleport: Render content to a different part of the DOM (perfect for modals)
• Suspense: Handle async component loading with fallback content
• Fragment: Multiple root elements in a component (no more wrapper divs!)

TypeScript First

Vue 3 was written in TypeScript, and it shows. The typing is excellent, with proper inference for props, emits, and slots. If you’re using TypeScript (and you should be), Vue 3 is a much better experience.

Migration Considerations

While Vue 3 is largely compatible with Vue 2, there are breaking changes to be aware of. Filters are removed (use computed properties or methods). The event bus pattern ($on, $off) is gone (use mitt or tiny-emitter). The global API has changed. For gradual migration, Vue provides a migration build that runs Vue 2 code on Vue 3’s runtime with deprecation warnings.

Key Takeaways

• Vue 3 is a major evolution with the Composition API enabling better code organization
• Performance is significantly improved with the rewritten virtual DOM
• TypeScript support is now first-class
• Migration tools make upgrading feasible for existing projects

References

• Vue 3 Official Documentation
• Vue 3 Migration Guide