将其他数据推送到Angular.js中的File对象

Question

在Angular 1.x应用程序中，我有多个图像上传字段。当图像添加到字段时，我想将一些其他数据推送到FileList对象上。我已经尝试过了：

for (var i = 0; i < files.length; i++) {
     files[i].append("File", "default_image", true);
}

“文件”的格式如下：

FileList {0: File, 1: File, 2: File, length: 3}
0: File {name: "001.JPG", lastModified: 1521848990762, lastModifiedDate: Fri Mar 23 2018 23:49:50 GMT+0000 (Greenwich Mean Time), webkitRelativePath: "", size: 136430, …}
1: File {name: "002.JPG", lastModified: 1521848990788, lastModifiedDate: Fri Mar 23 2018 23:49:50 GMT+0000 (Greenwich Mean Time), webkitRelativePath: "", size: 136276, …}
2: File {name: "003.JPG", lastModified: 1521848990815, lastModifiedDate: Fri Mar 23 2018 23:49:50 GMT+0000 (Greenwich Mean Time), webkitRelativePath: "", size: 137365, …}
length: 3

我得到的错误是：

  

未捕获的TypeError：无法读取未定义的属性“ append”