save file from client-side webpage

demo: https://eligrey.com/demos/FileSaver.js/
source code: https://github.com/eligrey/FileSaver.js
background: https://developers.google.com/web/updates/2011/08/Saving-generated-files-on-the-client-side
implementation: https://codepen.io/davidelrizzo/pen/cxsGb

See also https://ourcodeworld.com/articles/read/189/how-to-create-a-file-and-generate-a-download-with-javascript-in-the-browser-without-a-server

and https://gist.github.com/liabru/11263260

https://stackoverflow.com/questions/13405129/javascript-create-and-save-file