Vue Expert (JavaScript)

For shared Vue concepts, defer to vue-expert:

• vue-expert/references/composition-api.md - Core reactivity patterns
• vue-expert/references/components.md - Props, emits, slots
• vue-expert/references/state-management.md - Pinia stores

Code Patterns

Component with JSDoc-typed props and emits

<script setup>
/**
 * @typedef {Object} UserCardProps
 * @property {string} name - Display name of the user
 * @property {number} age - User's age
 * @property {boolean} [isAdmin=false] - Whether the user has admin rights
 */

/** @type {UserCardProps} */
const props = defineProps({
  name:    { type: String,  required: true },
  age:     { type: Number,  required: true },
  isAdmin: { type: Boolean, default: false },
})

/**
 * @typedef {Object} UserCardEmits
 * @property {(id: string) => void} select - Emitted when the card is selected
 */
const emit = defineEmits(['select'])

/** @param {string} id */
function handleSelect(id) {
  emit('select', id)
}
</script>

<template>
  <div @click="handleSelect(props.name)">
    {{ props.name }} ({{ props.age }})
  </div>
</template>

Composable with @typedef, @param, and @returns

// composables/useCounter.mjs
import { ref, computed } from 'vue'

/**
 * @typedef {Object} CounterState
 * @property {import('vue').Ref<number>} count - Reactive count value
 * @property {import('vue').ComputedRef<boolean>} isPositive - True when count > 0
 * @property {() => void} increment - Increases count by step
 * @property {() => void} reset - Resets count to initial value
 */

/**
 * Composable for a simple counter with configurable step.
 * @param {number} [initial=0] - Starting value
 * @param {number} [step=1]    - Amount to increment per call
 * @returns {CounterState}
 */
export function useCounter(initial = 0, step = 1) {
  /** @type {import('vue').Ref<number>} */
  const count = ref(initial)

  const isPositive = computed(() => count.value > 0)

  function increment() {
    count.value += step
  }

  function reset() {
    count.value = initial
  }

  return { count, isPositive, increment, reset }
}

@typedef for a complex object used across files

// types/user.mjs

/**
 * @typedef {Object} User
 * @property {string}   id       - UUID
 * @property {string}   name     - Full display name
 * @property {string}   email    - Contact email
 * @property {'admin'|'viewer'} role - Access level
 */

// Import in other files with:
// /** @type {import('./types/user.mjs').User} */

Constraints

MUST DO

• Use Composition API with <script setup>
• Use JSDoc comments for type documentation
• Use .mjs extension for ES modules when needed
• Annotate every public function with @param and @returns
• Use @typedef for complex object shapes shared across files
• Use @type annotations for reactive variables
• Follow vue-expert patterns adapted for JavaScript

MUST NOT DO

• Use TypeScript syntax (no <script setup lang="ts">)
• Use .ts file extensions
• Skip JSDoc types for public APIs
• Use CommonJS require() in Vue files
• Ignore type safety entirely
• Mix TypeScript files with JavaScript in the same component

Output Templates

When implementing Vue features in JavaScript:

1. Component file with <script setup> (no lang attribute) and JSDoc-typed props/emits
2. @typedef definitions for complex prop or state shapes
3. Composable with @param and @returns annotations
4. Brief note on type coverage

Knowledge Reference

Vue 3 Composition API, JSDoc, ESM modules, Pinia, Vue Router 4, Vite, VueUse, Vitest, Vue Test Utils, JavaScript ES2022+