JSFiddle - React, Tailwind, and code Playground

HTML

<textarea cols="20" id="testtextbox" name="testtextbox" rows="2">test</textarea>

JavaScript

var newForm = $('<form></form>').append($("#testtextbox"))
var formdata = new FormData(newForm.get(0));

var xhr = new XMLHttpRequest();
xhr.open('POST', '/', true);
xhr.send(formdata);