vue中父子组件通过props和update:实现双向绑定（el-upload）

例子：
这里的prop是fileList

在子组件里，将fileList赋值给showFileList
并watch showFileList值的变化， emit(‘update:(属性名)’, (传递数据))

emit('update:fileList', state.showFileList)

......
      const stopWatchShowFileList = watch(
        () => state.showFileList,
        () => {
   
          emit('update:fileList', state.showFileList)
        },
        {
    deep: true }
      )

      onMounted(() => {
   
        state.showFileList = props.fileList.map((file) => {
   
          file.url = file.id ? `${
     window.$config.imgURL}${
     file.id}` : file.url
          return file
        })
        emit('change-upload-loading')
      })

      onBeforeUnmount(() => {
   
        // stopWatchFileList()
        stopWatchShowFileList()
      })

详细代码：
父组件

      <el-form-item
        class="hidden-lg-only hidden-md-only hidden-xl-only"
        label="产品图片"
        prop="productImageList"
        style="margin-top: 10px"
      >
        <template v-if="!formDisabled">
          <el-icon v-show="uploadLoading" class="is-loading">
            <vab-icon icon="loader-5-fill" />
          </el-icon>
          <upload
            v-model:file-list="form.fileList"
            :can-video="false"
            @change-upload-loading="changeUploadLoading"
            @fetch-data="fetchData"
          />
        </template>
        <imageList
          v-else-if="formDisabled && form.fileList.length"
          :key="form.id"
          ref="imageListRef"
          align="left"
          :file-list="form.fileList"
          :size="100"
          :video-icon-size="50"
          :wrap="true"
        /