访问数组中的项返回未定义

When iterating through an array of objects, the properties are always undefined. The function in my Angular component class is as such:

upload(): void {
    const { fileHandles, relatedThroughID }: { fileHandles: IFileHandle[], relatedThroughID: Guid } = this.form.value;

    const postData: IUploadPost = {
      base64Files: fileHandles.map(fileHandle => ({ data: fileHandle.base64, extension: fileHandle.extension })),
      relatedThroughID: relatedThroughID.toString(),
    };
  }

这是记录结果的屏幕截图，因为我不敢相信自己所看到的-第二个log语句中的值是未定义的。

If I access an item by its index, the properties are also undefined. What in the world is happening here, and what can I do to fix it? I've never encountered a problem like this before.