Vue.js Composition API

Vue 3's Composition API isn't just a syntax change; it's a fundamental shift in how we think about state and logic reuse.

For years, the Vue Options API (data, methods, mounted, etc.) served us well. It was easy to learn and structured. However, as components grew complex, we hit a wall. Logic for a single feature—say, "Search"—would be scattered across `data`, `methods`, and `created`. To understand how search worked, you had to jump up and down the file 50 times. The Composition API solves this by allowing us to group code by feature rather than by option.

Composables over Mixins

The killer feature of the Composition API is "Composables". In Vue 2, we used Mixins to reuse logic, but Mixins were dangerous—they created namespace collisions and opaque data sources. A Composable is simply a function that leverages Vue's reactivity system. You import it, call it, and it returns exactly what you need. `useSearch()`, `usePagination()`, `useTheme()`. It is explicit, typed, and easy to unit test in isolation.

Another benefit is TypeScript support. The Options API relied heavily on `this` context, which is notoriously difficult for TypeScript to infer correctly. The Composition API sits naturally with functional programming patterns. Variables/refs are declared clearly, and types flow through them without complex hacks. If you are building enterprise Vue apps in 2025, TypeScript + Composition API is the gold standard.

Ref vs Reactive

A common stumbling block is choosing between `ref()` and `reactive()`. A good rule of thumb: use `ref` for primitives (strings, numbers, booleans) and `reactive` for distinct objects where the properties change together. However, many developers prefer using `ref` everywhere for consistency, accessing `.value` to make it clear that an unwrap is happening. Whichever structure you choose, stick to it across your team to avoid cognitive overhead.

Transitioning takes time. You don't have to rewrite your entire app. Vue 3 supports both APIs simultaneously. Start using Composition API for new, complex components, or when you find yourself needing to extract logic. Once you feel the freedom of `script setup`, you'll likely never want to go back to the limitations of `export default {}`.