gt-agent-company/.cursor/skills/vue/references/components-emits.md

name, description

name	description
component-events-emits	Emit and handle custom events from child to parent components

Component Events

Components emit custom events to communicate with parent components.

Emitting Events

Use $emit in templates or defineEmits in script:

<script setup lang="ts">
const emit = defineEmits(['inFocus', 'submit'])

function handleClick() {
  emit('submit')
}
</script>

<template>
  <button @click="$emit('inFocus')">Focus</button>
  <button @click="handleClick">Submit</button>
</template>

Type-Based Declaration (Recommended)

<script setup lang="ts">
// Call signature syntax
const emit = defineEmits<{
  (e: 'change', id: number): void
  (e: 'update', value: string): void
}>()

// Named tuple syntax (3.3+, more concise)
const emit = defineEmits<{
  change: [id: number]
  update: [value: string]
}>()

// Usage
emit('change', 123)
emit('update', 'hello')
</script>

Event Arguments

Pass additional arguments to events:

<script setup lang="ts">
const emit = defineEmits<{
  increaseBy: [amount: number]
}>()

function increase() {
  emit('increaseBy', 5)
}
</script>

Parent receives arguments:

<!-- Inline handler -->
<MyButton @increase-by="(n) => count += n" />

<!-- Method handler -->
<MyButton @increase-by="increaseCount" />

function increaseCount(n: number) {
  count.value += n
}

Event Validation

Validate event payloads with object syntax:

<script setup lang="ts">
const emit = defineEmits({
  // No validation
  click: null,
  
  // Validate submit event
  submit: ({ email, password }: { email: string; password: string }) => {
    if (email && password) {
      return true
    }
    console.warn('Invalid submit payload!')
    return false
  }
})
</script>

Listening to Events

Use v-on or @ shorthand:

<MyComponent @some-event="handleEvent" />

<!-- With .once modifier -->
<MyComponent @some-event.once="handleOnce" />

Event Name Casing

• Emit in camelCase
• Listen in kebab-case

emit('someEvent')

<MyComponent @some-event="handler" />

Important Notes

• Component events do NOT bubble (unlike DOM events)
• Only direct child events can be listened to
• For sibling/deeply nested communication, use provide/inject or state management