Error in file upload using Jquery & Ajax

I am trying to upload files using jQuery and AJAX. I have used FormData object which is supported in HTML5. I am using IE11. Below is my code:

<form id="tradeForm" method="post" action="/trade.action?method=addTrade" enctype="multipart/form-data">
    Trade Type : <input type="text" id="tradeType" name="tradeType">
    Trade Document : <input type="file" id="attachedFile" name="attachment" size="40">
</form>

I've tried using $.post:

$("#tradeForm").submit(function(event){
    event.preventDefault();
    var form = $(this);
    var formData = new FormData(form);
    url = form.attr("action");

    $.post(url, formData, function(data) {
        console.log(data);
    });
});

And also using $.ajax

$("#tradeForm").submit(function(event){
    event.preventDefault();
    var form = $(this);
    var formData = new FormData(form);
    url = form.attr("action");

    $.ajax({
        url: url,
        type: "POST",
        data: formData,
        processData: false,  // tell jQuery not to process the data
        contentType: false   // tell jQuery not to set contentType
    }).done(function(data) {
        console.log(data);
    });
});

I get the following errors:

Argument not optional

When $.post method is used

SCRIPT7002: XMLHttpRequest: Network Error 0x2ef3, Could not complete the operation due to error 00002ef3

When $.ajax method is used. How can I solve these errors?