serializeArray输入数据不会通过动态添加传递思想ajax

function SendData(){
    var postData = $("#xForm").serializeArray();
    $.ajax({
    type: "POST",
    url: "mail.php",
    data: postData,
    success:function(data){
        console.log(data);
    },
    error: function(jqXHR, textStatus, errorThrown) 
    {
    console.log("failure send");
    }
    });
}


    $('#sub-comfirm').on('submit',  function (e){
        e.preventDefault();
        SendData();
    });



function PostImgCreate(imgValue){
    var pImg = $("#mydata");

    var inputblock = "";
    inputblock += '<input type="hidden" id="canvasData" name="canvasData">';
    pImg.html(inputblock);

    var elem = document.getElementById("canvasData");
    elem.value = imgValue;
}
function SendData(){
    var postData = $("#xFo