I dont know if it is a good idear but: Should we define some constants instead of literals? eg.:
Not sure about naming conventions
```js
if (type === CollectionFS.invalidFileSize)
if (type === CollectionFS.disallowedExtension)
if (type === CollectionFS.errorContentType)
```
would contain an integer code?
```fs
CollectionFS = { errorContentType = 01; }
```