How to upload a file without using a form with Ajax

Simple to follow, the best tutorial I was able to find for my need (thanks) - I have a question regarding the example: How do I capture the ".then((data) =>" to a text string? Searched for a very long time but could not find a working solution.

Great tutorial, thank you. I suggest revising the title to: "How to upload a file with Ajax without using a form"

Great video but i have some issues concerning the filereader object that i can not understand when we are doing a file upload.