JavaScript implements asynchronous submission of form data

<div class="container">
       <form class="form-horizontal" onsubmit="return false;">
           <div class="form-group">
               <label class="control-label col-md-3">Name:</label>
               <div class="col-md-4">
                   <input type="type" name="txtname" value=" " class="form-control" id="txtName"/>
               </div>
           </div>
           <div class="form-group">
               <label class="control-label col-md-3">Gender:</label>
               <div class="col-md-4">
                   <select class="form-control" name="cboSex" id="cboSex">
                       <option>Male</option>
                       <option>Female</option>
                   </select>
               </div>
           </div>
           <div class="form-group">
               <label class="control-label col-md-3">Address:</label>
               <div class="col-md-4">
                   <textarea class="form-control" name="txtAddress" id="txtAddress"></textarea>
               </div>
           </div>
           <div class="form-group">
               <button class="btn btn-primary col-md-offset-4" onclick="getVal()">Get the value of the form</button>
               <button class="btn btn-primary" onclick="postgetData()">Submit data</button>
               <button class="btn btn-success" onclick="getData()">Get data</button>
           </div>
       </form>
</div>

function postgetData() {
            var xhr;
            if (window.XMLHttpRequest) {
                xhr = new XMLHttpRequest();
            } else {
                xhr = new ActiveXObject("microsoft.XMLHTTP");
            }
            xhr.open("post", "/JQuery/getDataRequest", true);
            xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
            var yy = "name=" + document.getElementById("txtName")
                .value + "&sex=" + document.getElementById("cboSex")
                .value + "&address=" + document.getElementById("txtAddress").value;
            xhr.send(yy);
            xhr.onreadystatechange = function () {
                if (xhr.status == 200 && xhr.readyState == 4) {
                    var txt = xhr.responseText;
                    console.log(txt);
                }
            }
        }

public ActionResult getDataRequest()
        {
            string name = Request.Form["name"];
            string sex = Request.Form["sex"];
            string address = Request.Form["address"];
            string str = name + "&" + sex + "&" + address + "&" + "Request can only receive post data";
            return Content(str);
        }