How to to save txt file on server in HTML/JS?

I’m making signup form stuff and I want to save data to server and I got this code :

function Signup()
   {
     var text = "hello world",
   blob = new Blob([text], { type: 'text/plain' }),
   anchor = document.createElement('a');

anchor.download = "hello.txt";
anchor
anchor.href = (window.webkitURL || window.URL).createObjectURL(blob);
anchor.dataset.downloadurl = ['text/plain', anchor.download, anchor.href].join(':');
anchor.click();
   }

But its download file and I’m wondering how to save/download it to server.