HTML5 finally provides a standard way to interact with local files, via the File API specification. As example of its capabilities, the File API could be used to create a thumbnail preview of images as they’re being sent to the server, or allow an app to save a file reference while the user is offline. Additionally, you could use client-side logic to verify an upload’s mimetype matches its file extension or restrict the size of an upload.
The spec provides several interfaces for accessing files from a ‘local’ filesystem:
File– an individual file; provides readonly information such as name, file size, mimetype, and a reference to the file handle.
FileList– an array-like sequence of
<input type="file" multiple>or dragging a directory of files from the desktop).
Blob– Allows for slicing a file into byte ranges.
When used in conjunction with the above data structures, the
XMLHttpRequest‘s event model.