The slice is used to create a new Blob object containing the data in the specified range of bytes of the source Blob.
An object of this type is 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. It's also used for a list of files dropped into web content when using the drag and drop API; see the DataTransfer object for details on this usage.
A Blob object represents a file-like object of immutable, raw data. Blobs represent data that isn't necessarily in a JavaScript-native format. The File interface is based on Blob, inheriting blob functionality and expanding it to support files on the user's system.