Create and modify a file in JQuery

I need to create files on the server, since they are invisible to the client, but what I have found allows me to create the file and download it to the client, which I do not want. One of the methods I saw was this:

var contenidoDeArchivo = "Hola Mundo!";
var elem = document.getElementById('descargar');

elem.download = "archivo.txt";
elem.href = "data:application/octet-stream," 
                 + encodeURIComponent(contenidoDeArchivo);

What is an answer to the question: How to create a text file with javascript? but apparently it does not allow to customize the file settings and download it to the client.

Is there any way to create files without downloading them and only create them in the application folder?