Vue Component Priming

Note: This command references the nuxt:nuxt skill for progressive disclosure of additional Vue patterns and library-specific documentation.

Script Setup Syntax

Use <script setup lang="ts"> for component script sections.

Props

Use TypeScript type-based syntax for defineProps():

// ✅ Correct: Type-based with destructuring and inline defaults
const {
  title,
  count = 0,
  enabled = true,
} = defineProps<{
  title: string
  count?: number
  enabled?: boolean
}>()

// ✅ Correct: No props used in script
defineProps<{
  title: string
}>()

// ❌ Wrong: Runtime PropType syntax
import type { PropType } from "vue"
defineProps({
  items: {
    type: Array as PropType<string[]>,
    required: true,
  },
})

Emits

Use type-based syntax for defineEmits:

// ✅ Correct: Type-based emits
const emit = defineEmits<{
  update: [value: string]
  close: []
}>()

// ❌ Wrong: Runtime array syntax
const emit = defineEmits(["update", "close"])

Event Handler Typing

When emitting events with event objects, use appropriate event types:

// ✅ Correct: Typed event handlers
const emit = defineEmits<{
  click: [event: MouseEvent]
  keypress: [event: KeyboardEvent]
  input: [event: InputEvent]
  submit: [event: SubmitEvent]
}>()

// Usage in template
<button @click="emit('click', $event)">Click me</button>
<input @keypress="emit('keypress', $event)" />

v-model

USE defineModel() for v-model implementations:

// ✅ Correct: Using defineModel
const modelValue = defineModel<string>()

// With options
const modelValue = defineModel<string>({ required: true })

// ❌ Wrong: Manual prop + emit
const props = defineProps<{ modelValue: string }>()
const emit = defineEmits<{ "update:modelValue": [value: string] }>()

Component Structure

Template Placement

Place <template> section first, before <script> and <style>:

<!-- ✅ Correct order -->
<template>
  <div>{{ title }}</div>
</template>

<script setup lang="ts">
const { title } = defineProps<{ title: string }>()
</script>

<style scoped>
div {
  color: blue;
}
</style>

Component Naming

• Use multi-word component names except for Nuxt pages and layouts
• Examples: UserProfile.vue, SearchBar.vue (not User.vue, Search.vue)
• Exception: pages/index.vue, pages/about.vue, layouts/default.vue

Template Directives

v-for Loops

Use key in v-for loops and prefer of over in:

<!-- ✅ Correct -->
<li v-for="user of users" :key="user.id">{{ user.name }}</li>

<!-- ❌ Wrong: Missing key -->
<li v-for="user of users">{{ user.name }}</li>

<!-- ❌ Wrong: Using 'in' instead of 'of' -->
<li v-for="user in users" :key="user.id">{{ user.name }}</li>

Prop Binding Shorthand

Use shorthand syntax when passing props with same name as variable:

<!-- ✅ Correct: Shorthand -->
<UserCard :username :avatar :bio />

<!-- ❌ Wrong: Verbose when unnecessary -->
<UserCard :username="username" :avatar="avatar" :bio="bio" />

Reactivity and State

Reactive References

PREFER ref() for reactive state instead of reactive():

// ✅ Preferred: Using ref
const count = ref(0)
const user = ref({ name: "Alice", age: 30 })

// ❌ Less preferred: Using reactive (loses reactivity on destructure)
const state = reactive({ count: 0 })

Auto-Imported Vue APIs

Don't manually import these in Nuxt projects - they're auto-imported:

Reactivity:

• ref - Reactive primitive values
• reactive - Reactive objects
• computed - Computed values
• watch - Watch reactive values

Lifecycle:

• onMounted - Component mounted
• onUnmounted - Component unmounted
• onBeforeMount, onBeforeUnmount, etc.

Component APIs:

• defineProps - Define props (type-based)
• defineEmits - Define emits (type-based)
• defineModel - Define v-model (type-based)

Utilities:

• useId - Generate unique IDs for accessibility/form elements (SSR-safe)

Component Organization

Logical Grouping

PREFER to group by logical concerns rather than by type:

// ✅ Preferred: Grouped by feature/concern
<script setup lang="ts">
// User authentication concern
const user = ref(null)
const isAuthenticated = computed(() => !!user.value)
async function login() { /* ... */ }

// Search functionality concern
const searchQuery = ref('')
const searchResults = computed(() => /* ... */)
function handleSearch() { /* ... */ }
</script>

// ❌ Less preferred: Grouped by type
<script setup lang="ts">
// All refs
const user = ref(null)
const searchQuery = ref('')

// All computed
const isAuthenticated = computed(() => !!user.value)
const searchResults = computed(() => /* ... */)

// All functions
async function login() { /* ... */ }
function handleSearch() { /* ... */ }
</script>

Styling Strategy

Check package.json for @nuxtjs/tailwindcss:

If Tailwind Installed

<template>
  <div class="flex items-center gap-4 p-4 bg-gray-100 dark:bg-gray-800">
    <!-- Use Tailwind utilities -->
    <!-- Arbitrary variants: [&::-webkit-scrollbar]:w-1.5 -->
    <!-- Custom properties: @theme directive -->
  </div>
</template>

If NO Tailwind

Use <style scoped>. Prefer short, simple class names - scoped styles eliminate need for BEM:

<!-- ✅ Preferred -->
<template>
  <div class="card">
    <div class="header">Title</div>
    <div class="content">Body</div>
  </div>
</template>

<style scoped>
.card { padding: 1rem; }
.header { font-weight: bold; }
.content { flex: 1; }
</style>

<!-- ❌ Avoid: BEM with scoped styles -->
<div class="user-card">
  <div class="user-card__header">Title</div>
</div>

VueUse Composables (If Installed)

Check package.json for @vueuse/core or @vueuse/nuxt:

PREFER VueUse composables over custom implementations for common tasks:

// ✅ Preferred: Using VueUse (if installed)
import { useLocalStorage, useMouse, useWindowSize } from "@vueuse/core"
const token = useLocalStorage("auth-token", "")

// ❌ Avoid: Custom implementation when VueUse exists
const token = ref(localStorage.getItem("auth-token") || "")
watch(token, (val) => localStorage.setItem("auth-token", val))

Common VueUse Patterns

State:

• useToggle, useCounter, useLocalStorage, useSessionStorage

DOM:

• useMouse, useScroll, useElementVisibility, useIntersectionObserver, useResizeObserver

Browser:

• useClipboard, useMediaQuery, useDark, usePreferredDark, useGeolocation

Utilities:

• refDebounced, useDebounceFn, refThrottled, useThrottleFn, useInterval, useTimeout

The nuxt:nuxt skill provides detailed VueUse reference when installed.

Accessibility

• Use semantic HTML: <button>, <nav>, <main>, <article>
• Add ARIA attributes to interactive elements
• Ensure keyboard navigation (tab order, enter/space handlers)

TypeScript Types

• Place component prop interfaces in same file or /types directory
• Use PascalCase: ButtonProps, CardProps, UserState
• Don't use as any - prefer type guards or as unknown as Type

Performance Patterns

Computed vs Methods

Use computed() for derived state (cached):

// ✅ Cached, only recalculates when dependencies change
const fullName = computed(() => `${firstName.value} ${lastName.value}`)

// ❌ Recalculates on every render
const getFullName = () => `${firstName.value} ${lastName.value}`

Static Content

Use v-once for static content that never changes:

<div v-once>
  <h1>Static Header</h1>
  <p>This content never changes</p>
</div>

Expensive Lists

Use v-memo for expensive lists with stable data:

<div v-for="item of list" :key="item.id" v-memo="[item.id]">
  <!-- Expensive rendering -->
</div>

Template Best Practices

Conditional Rendering

• Use v-show for frequent toggles
• Use v-if for conditional rendering

<!-- Frequent toggling: keep in DOM -->
<div v-show="isVisible">Toggle me often</div>

<!-- Conditional: add/remove from DOM -->
<div v-if="hasPermission">Render only when needed</div>

Event Handling

<!-- Inline handlers for simple cases -->
<button @click="count++">Increment</button>

<!-- Method refs for complex logic -->
<button @click="handleSubmit">Submit</button>

<!-- Modifiers -->
<button @click.prevent="handleClick">Prevent Default</button>
<input @keyup.enter="handleEnter" />

Slots

<!-- Basic slot -->
<template>
  <div class="card">
    <slot />
  </div>
</template>

<!-- Named slots -->
<template>
  <div class="card">
    <header><slot name="header" /></header>
    <main><slot /></main>
    <footer><slot name="footer" /></footer>
  </div>
</template>

<!-- Scoped slots -->
<template>
  <ul>
    <li v-for="item of items" :key="item.id">
      <slot :item="item" />
    </li>
  </ul>
</template>

Provide/Inject

For dependency injection:

// Parent component
provide("theme", "dark")
provide("api", apiClient)

// Child component (any depth)
const theme = inject("theme")
const api = inject("api")

// With TypeScript
import type { InjectionKey } from "vue"

interface Theme {
  mode: "light" | "dark"
}

const themeKey: InjectionKey<Theme> = Symbol("theme")

// Provide
provide(themeKey, { mode: "dark" })

// Inject
const theme = inject(themeKey)

Lifecycle Hooks

// Setup (reactive state initialization)
const count = ref(0)

// Mounted (DOM available)
onMounted(() => {
  console.log("Component mounted")
})

// Before unmount (cleanup)
onBeforeUnmount(() => {
  // Remove event listeners, clear timers, etc.
})

// Unmounted
onUnmounted(() => {
  console.log("Component unmounted")
})

// Watch effect (runs immediately and on dependencies change)
watchEffect(() => {
  console.log(`Count is ${count.value}`)
})

// Watch specific value
watch(count, (newValue, oldValue) => {
  console.log(`Count changed from ${oldValue} to ${newValue}`)
})

Template Refs

<template>
  <input ref="inputRef" />
  <MyComponent ref="componentRef" />
</template>

<script setup lang="ts">
const inputRef = ref<HTMLInputElement>()
const componentRef = ref<InstanceType<typeof MyComponent>>()

onMounted(() => {
  inputRef.value?.focus()
})
</script>