The FileList interface represents an object of this type returned by the files property of the HTML input element; this lets you access the list of files selected with the <input type='file'> element.
FileList
files
<input type='file'>
MDN Reference
The length read-only property of the FileList interface returns the number of files in the FileList.
length
The item() method of the FileList interface returns a File object representing the file at the specified index in the file list.
item()