Change Asp Button class after file upload

Question

I want to enable a disabled button after the file uploads. However, I can not seem to get it enabled.

<asp:Content runat="server" ID="BodyContent" ContentPlaceHolderID="MainContent">
    <script type="text/javascript">
        $('#FileUpload').on('change', function (e) {
            Document.getElementById("btnUploadFile").className = "btn standard-gradient";
        });
    </script>

    <asp:FileUpload ID="FileUpload" runat="server" class="btn"/>

    <asp:Button runat="server" ID="btnUploadFile" Text="Upload File" OnClick="btnUploadFile_OnClick" class="btn standard-gradient disabled"/>
</asp:Content>

Answer 1

try this script:

<script type = "text/javascript" >
    $('#FileUpload').on('change', function (e) {
        var btn = $("#btnUploadFile");
        if (btn.prop("disabled")) { $("#btnUploadFile").prop('disabled', '') } 
        else { $("#btnUploadFile").prop('disabled', 'disabled') }
    });
</script>

Check this JSFIDDLE as a sample.

HTML

<button id="FileUpload">file</button>
<button id="btnUploadFile">btn</button>

JS

$('#FileUpload').on('click', function (e) {
    var btn = $("#btnUploadFile");
    if ( btn.prop( "disabled" ) ){
        $("#btnUploadFile").prop('disabled', '')
    }
    else {$("#btnUploadFile").prop('disabled', 'disabled')}
});