Send POST request in javascript popup window

Question

I'm trying to send POST request to javascript pop-up. I was able to do it using a new tab, but would like to do using a pop-up.

    var mapForm = document.createElement("form");
    mapForm.target = target;
    mapForm.method = method;
    mapForm.action = url;

    if (data) {
        for (var key in data) {
            var input = document.createElement("textarea");
            input.name = key;
            input.value = data[key];
            mapForm.appendChild(input);
        }
    }
    mapForm.style.display = "none";
    document.body.appendChild(mapForm);

    mapForm.submit();