upload method to select a file in the File open dialog box and
upload it to the static/files directory in the server folder.
When saving the file on the server, the file name is changed by the Werkzeug secure_filename function and then the current date is added to it. See http://werkzeug.pocoo.org/docs/0.14/utils/
options parameter is an object that may have the following attributes:
callback- is a callback function that is executed when the file is downloaded. It is passed, as parameters, the name of the file stored on the server, the name of the downloaded file and the path to the folder where the file was saved.
show_progress- if true and the uploaded file is large, the progress bar will be displayed. the defaul value is true
accept- the attribute specifies the types of files that can be submitted through a file upload, see Accept string
Please note that the
accept attribute specifies only types of files that
can be picked up by the user in the browser.
The server checks all uploaded files for compliance with the Upload file extensions attribute of the Project parameters.