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.

1. 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']

2. 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
  }
}

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.