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ViewsVue 3 defineEmits breaks defineProps types
I'm using Vue 3 and TS 4.4. I've got a component that defines its prop types with defineProps. When I add a call to defineEmits, VS Code starts telling me my props variable doesn't exist in the component template. Here's the source code:
<script setup lang="ts">
import { defineProps, defineEmits, VueElement, defineComponent } from "vue";
const emit = defineEmits<{
"update:checked": boolean;
}>();
const props = defineProps<{
label?: VueElement | string;
checked?: boolean;
}>();
</script>
<template>
<label>
<input
type="checkbox"
:checked="props.checked"
@change="(event) => emit('update:checked', (event.target as any)?.checked)"
/>
{{ props.label }}
</label>
</template>
And a couple of screenshots to better show what I'm seeing in VS Code. This is after adding defineEmits:
And this is without defineEmits:
What is the correct way to define types for both props and emits?
·
Juan Pablo Isaza
1 answers
Answer question0
The defineEmits<T>() generic argument is essentially a TypeScript interface that defines only functions, which receive a specific event name and optional arguments:
interface Emits {
(e: __EVENT1_NAME__ [, arg1: __ARG1_TYPE__ [, arg2: __ARG2_TYPE__]]...): void
(e: __EVENT2_NAME__ [, arg1: __ARG1_TYPE__ [, arg2: __ARG2_TYPE__]]...): void
}
Examples:
// as inline type
const emits = defineEmits<{
(eventName: 'hover', hovering: boolean): void
(eventName: 'changed', newValue: number, id: string): void
}>()
// as interface
interface Emits {
(eventName: 'hover', hovering: boolean): void
(eventName: 'changed', newValue: number, id: string): void
}
const emits = defineEmits<Emits>()
// as type alias
type Emits = {
(eventName: 'hover', hovering: boolean): void
(eventName: 'changed', newValue: number, id: string): void
}
const emits = defineEmits<Emits>()
For your update:checked event, the code should look similar to the following:
// as inline type
const emits = defineEmits<{
(e: 'update:checked', checked: boolean): void
}>()
// as interface
interface Emits {
(e: 'update:checked', checked: boolean): void
}
const emits = defineEmits<Emits>()
// as type alias
type Emits = {
(e: 'update:checked', checked: boolean): void
}
const emits = defineEmits<Emits>()
·
Juan Pablo Isaza
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