javascript - jQuery iframe file upload

Question

Im building a file upload with jQuery, but Im getting a jQuery error trying to set the attributes of the form:

$(document).ready(function () {
    $("#formsubmit").click(function () {

        var iframe = $('<iframe name="postframe" id="postframe" class="hidden" src="about:none" />');

        $('div#iframe').append(iframe);

        $('#theuploadform').attr("action", "/ajax/user.asmx/Upload")
        $('#theuploadform').attr("method", "post")
        $('#theuploadform').attr("userfile", $('#userfile').val())
        $('#theuploadform').attr("enctype", "multipart/form-data")
        $('#theuploadform').attr("encoding", "multipart/form-data")
        $('#theuploadform').attr("target", "postframe")
        $('#theuploadform').submit();
        //need to get contents of the iframe

        $("#postframe").load(
            function () {
                iframeContents = $("iframe")[0].contentDocument.body.innerHTML;
                $("div#textarea").html(iframeContents);
            }
        );
    }
);


<div id="uploadform">
    <form id="theuploadform" action="">
        <input id="userfile" name="userfile" size="50" type="file" />
        <input id="formsubmit" type="submit" value="Send File" />
    </form>
</div>

<div id="iframe" style="width: 0px; height: 0px; display: none;">
</div>

<div id="textarea">
</div>

Answer 1

I found the solution. This code works:

<script type="text/javascript">

    $(document).ready(function () {

        $("#formsubmit").click(function () {

            var iframe = $('<iframe name="postiframe" id="postiframe" style="display: none"></iframe>');

            $("body").append(iframe);

            var form = $('#theuploadform');
            form.attr("action", "/upload.aspx");
            form.attr("method", "post");

            form.attr("encoding", "multipart/form-data");
            form.attr("enctype", "multipart/form-data");

            form.attr("target", "postiframe");
            form.attr("file", $('#userfile').val());
            form.submit();

            $("#postiframe").load(function () {
                iframeContents = this.contentWindow.document.body.innerHTML;
                $("#textarea").html(iframeContents);
            });

            return false;

        });

    });

</script>


<form id="theuploadform">
    <input id="userfile" name="userfile" size="50" type="file" />
    <input id="formsubmit" type="submit" value="Send File" />
</form>

<div id="textarea">
</div>