Vue 3 Composition API, script setup macros, reactivity system, and built-in components. Use when writing Vue SFCs, defineProps/defineEmits/defineModel, watchers, or using Transition/Teleport/Suspense/KeepAlive.
Based on Vue 3.5. Always use Composition API with
<script setup lang="ts">.
<script setup lang="ts"> over <script>shallowRef over ref if deep reactivity is not needed| Topic | Description | Reference |
|---|---|---|
| Script Setup & Macros | <script setup>, defineProps, defineEmits, defineModel, defineExpose, defineOptions, defineSlots, generics | script-setup-macros |
| Reactivity & Lifecycle | ref, shallowRef, computed, watch, watchEffect, effectScope, lifecycle hooks, composables | core-new-apis |
| Topic | Description | Reference |
|---|---|---|
| Built-in Components & Directives | Transition, Teleport, Suspense, KeepAlive, v-memo, custom directives | advanced-patterns |
<script setup lang="ts">
import { computed, onMounted, ref, watch } from 'vue'
const props = defineProps<{
title: string
count?: number
}>()
const emit = defineEmits<{
update: [value: string]
}>()
const model = defineModel<string>()
const doubled = computed(() => (props.count ?? 0) * 2)
watch(() => props.title, (newVal) => {
console.log('Title changed:', newVal)
})
onMounted(() => {
console.log('Component mounted')
})
</script>
<template>
<div>{{ title }} - {{ doubled }}</div>
</template>
// Reactivity
import { computed, reactive, readonly, ref, shallowRef, toRef, toRefs, toValue } from 'vue'
// Watchers
import { onWatcherCleanup, watch, watchEffect, watchPostEffect } from 'vue'
// Lifecycle
import { onBeforeMount, onBeforeUnmount, onBeforeUpdate, onMounted, onUnmounted, onUpdated } from 'vue'
// Utilities
import { defineAsyncComponent, defineComponent, nextTick } from 'vue'