为什么 prop 中的 boolean 属性没有指定的时候，接收到的值是 false 而不是 undefined？(Why, when a boolean property in a prop is not specified, does it receive a value of false instead of undefined?)

[QinHang-Git]

代码如下（The code is as follows:）

<script setup lang="ts">
import { ref } from 'vue'

const msg = ref('Hello World!')
const props = defineProps<{ a?: boolean, b?:string }>();
console.log(props);
</script>

<template>
  <h1>{{ msg }}</h1>
  <input v-model="msg" />
</template>

这里打印出来 a 是 false , b 是 undefined。 请问为什么这样设计？（Here, 'a' prints out is false and 'b' is undefined. May I ask why such a design was chosen?）

我是想实现这样一个组件，才遇到了这个问题。（I encountered this issue while trying to implement a specific component.）
经过简化的场景如下：（A simplified scenario is as follows:）

<script setup lang="ts">
import { computed } from 'vue';
import { TableProps, ElTable, ElTableColumn } from 'element-plus';

const props = defineProps<
  Partial<TableProps<any>> & {
    title: '标题';
  }
>();
const elTableProps = computed(() => {
  const { title, ...tableProps } = props;
  console.log(tableProps);
  return tableProps;
});
</script>

<template>
  <div>
    <div>{{ title }}</div>
    <el-table ref="elTableRef" v-bind="elTableProps">
      <el-table-column label="ddddd"></el-table-column>
    </el-table>
  </div>
</template>

我的组件为了兼容 element plus 的原本的属性，且在父组件中能够得到更好的ts提示，因此，我的prop继承了原本的TableProps，TableProps中有很多属性都是boolean类型，我在父组件中没有传递的话，在我这个组件中会转换成false，进而我再传递到 elTable中后，覆盖掉了一些默认为true的属性，导致出现了一系列的问题。（In order to maintain compatibility with the original attributes of Element Plus and provide better TypeScript hints in the parent component, my component inherits the original TableProps. Within TableProps, there are numerous properties that are boolean typed. If these properties are not passed from the parent component, they will default to false in my component. Subsequently, when I pass these properties to the elTable, they override some default properties which are initially set to true, thus resulting in a series of issues.）

[Justineo]

See:

• Boolean props default value is not undefined #5863
• Unexpected result from defineProps() #9876
• Boolean v-model doesn't default to undefined when not set #9882

[QinHang-Git]

thankyou