sending form to hiiden iframe

form.js

//copyed from https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Forms/Sending_forms_through_JavaScript
// Let's create the iFrame used to send our data
var iframe = document.createElement("iframe");
iframe.name = "myTarget";

// Next, attach the iFrame to the main document
window.addEventListener("load", function () {
  iframe.style.display = "none";
  document.body.appendChild(iframe);
});

// This is the function used to actually send the data
// It takes one parameter, which is an object populated with key/value pairs.
function sendData(data) {
  var name,
      form = document.createElement("form"),
      node = document.createElement("input");

  // Define what should happen when the response is loaded
  iframe.addEventListener("load", function () {
    alert("Yeah! Data sent.");
  });
    
  form.action = "http://www.cs.tut.fi/cgi-bin/run/~jkorpela/echo.cgi";
  form.target = iframe.name;

  for(name in data) {
    node.name  = name;
    node.value = data[name].toString();
    form.appendChild(node.cloneNode());
  }

  // To be sent, the form needs to be attached to the main document.
  form.style.display = "none";
  document.body.appendChild(form);

  form.submit();

  // But once the form is sent, it's useless to keep it.
  document.body.removeChild(form);
}