How to upload multi images to server?

Hi all,

so, i will try upload image to server using File Transfer and now i need upload multi images to server

how can i using file transfer to upload multi images when i load form Library (i using Image Picker for it.)

and how can I use transfer to upload multiple files at the same time? or can i using Observable or toPromise for it?

please help me if you have a solution for it thanks you!