defineEmits

defineEmits 是一个 Vue 3 的 API，用于为组件声明可触发的事件。它接受一个对象作为参数，对象的属性名为事件名称，属性值为事件的参数类型。
通过使用 defineEmits，我们可以在组件中使用 $emit 方法触发声明的事件，并且在编写组件时，编辑器可以根据声明的事件提供自动补全和类型检查的功能。
例如，我们可以在组件中使用以下代码声明两个事件：
import { defineComponent, defineEmits } from 'vue'

const MyComponent = defineComponent({
emits: ['increment', 'decrement'],
setup(props, { emit }) {
function handleClick() {
emit('increment')
}

return {
handleClick
}
}
})
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在这个例子中，我们声明了 increment 和 decrement 两个事件，并在组件的 setup 函数中使用 emit 方法分别触发这两个事件。在其他地方使用这个组件时，我们可以像这样监听这两个事件：
<MyComponent @increment="handleIncrement" @decrement="handleDecrement" />
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相关问题

defineemits

Emits is a term that is commonly used in programming and refers to the act of generating or producing something, often in the form of events or signals. In the context of event-driven programming, emitting refers to the process of sending or broadcasting an event to notify other parts of the program that a specific action or condition has occurred.
For example, in JavaScript, an event emitter is an object that can emit events and notify registered listeners when those events occur. The emitter emits events by triggering callbacks associated with those events.
Here's an example to illustrate the concept:
// Create an event emitter
const emitter = new EventEmitter();

// Register a listener for the 'click' event
emitter.on('click', () => {
console.log('Button clicked!');
});

// Emit the 'click' event
emitter.emit('click'); // Output: 'Button clicked!'
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In this example, the emitter object emits the 'click' event, which triggers the registered callback function and logs 'Button clicked!' to the console.
Related questions:

What are some programming languages or frameworks that commonly use event emitters?
How can I implement my own event emitter in a programming language?
Can you explain the difference between emitting and broadcasting events?

defineEmits defineProps

defineEmits and defineProps are options provided by Vue.js, a popular JavaScript framework for building user interfaces. These options are used in the configuration of a Vue component to define the events that the component can emit and the props that the component accepts.

defineEmits: This option is used to declare the custom events that a component can emit. It allows you to specify the names of the events that the component can trigger. By using this option, you are explicitly defining the events that the component emits, making it easier for other components or parent components to listen to these events and perform actions accordingly.

Example usage of defineEmits:
defineEmits: ['eventName']
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defineProps: This option is used to declare the props that a component accepts. Props are custom attributes that can be passed to a component from its parent component or from the parent template. By using defineProps, you define the expected props and their types, making it easier to enforce prop validation and ensure that the props are used correctly.

Example usage of defineProps:
defineProps: {
propA: {
type: String,
required: true
},
propB: {
type: Number,
default: 0
}
}
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In summary, defineEmits is used to declare custom events that a component can emit, while defineProps is used to declare the props that a component accepts. These options enhance the reusability and maintainability of Vue components by providing clear definitions for events and props.