Composable adalah fungsi yang mengenkapsulasi logika reaktif — mirip custom hooks di React.

// useCounter composable
function useCounter(initial = 0) {
  const count = ref(initial)
  const increment = () => count.value++
  const decrement = () => count.value--
  const reset = () => count.value = initial
  return { count, increment, decrement, reset }
}

const { count, increment, reset } = useCounter(0)

---template---
<span>{{ count }}</span>
<button @click="increment">+</button>
<button @click="reset">Reset</button>

Aturan Composable

• Nama diawali use (konvensi)
• Hanya dipanggil di setup() atau composable lain
• Bisa menggunakan semua Composition API (ref, computed, watch, lifecycle)