test.js

function mergeDocument() {

        // save the document in the internal tx format
        TXTextControl.saveDocument(TXTextControl.StreamType.InternalUnicodeFormat,
                                   function (e) {

            var serviceURL = "@Url.Action("Merge", "Home")";

            // send document to controller
            $.ajax({
                type: "POST",
                url: serviceURL,
                data: {
                    document: e.data // the template
                },
                success: successFunc,
                error: errorFunc
            });
        });
}

function successFunc(data, status) {
        // load the resulting document back into the editor
        TXTextControl.loadDocument(TXTextControl.StreamType.InternalUnicodeFormat, data);
}

function errorFunc() {
        alert("Error");
}