Add List Item with JSOM returns "Unknown Error"

Question

Having some trouble with a very basic use of the JSOM controls for adding list items.

My code:

    function submitClick(who, where, when, description, name, number) {

    //alert(who + where + when + description + name + number);
    var context = SP.ClientContext.get_current();
    var list = context.get_web().get_lists().getByTitle('*my list name*');

    var itemCreateInfo = new SP.ListItemCreationInformation();

    var oListItem = list.addItem(itemCreateInfo);
    oListItem.set_item('Who', who);
    oListItem.set_item('Where', where);
    oListItem.set_item('When', when);
    oListItem.set_item('Description', description);
    oListItem.set_item('Name', name);
    oListItem.set_item('Contact', number);
    oListItem.set_item('CreateDate', Date.now());
    oListItem.set_item('Title', Date.now().toString()); //column is hidden but required
    oListItem.update();

    context.load(oListItem);
    context.executeQueryAsync(onCreateListItemSuccess, onCreateListItemFailed);

    function onCreateListItemSuccess() {
        alert('yay');
    }
    function onCreateListItemFailed(sender, args) {
        alert('failed. ' + args.get_message() + '\n' + args.get_stackTrace());
    }
}

As you can see, it's just about as basic as it gets- Problem is, the ProcessQuery call always returns this:

{
"SchemaVersion":"15.0.0.0","LibraryVersion":"16.0.21010.12006","ErrorInfo":{
"ErrorMessage":"Unknown Error","ErrorValue":null,"TraceCorrelationId":"71d0ad9f-b05d-b000-95bc-b4c0e452fdc8","ErrorCode":-1,"ErrorTypeName":"Microsoft.SharePoint.Client.UnknownError"
}

That's right- "Unknown Error" and no ErrorValue. What's going on here?

Answer 1

CreateDate should be a Date column, then should set with a date object in JavaScript, please modify as below:

    <script type="text/javascript">
        function CreateListItem() {

            var context = SP.ClientContext.get_current();
            var list = context.get_web().get_lists().getByTitle('CustomList');

            var itemCreateInfo = new SP.ListItemCreationInformation();

            var oListItem = list.addItem(itemCreateInfo);
            const timeElapsed = Date.now();
            const today = new Date(timeElapsed);
            oListItem.set_item('CreateDate', today);
            oListItem.set_item('Title', Date.now().toString()); //column is hidden but required
            oListItem.update();

            context.load(oListItem);
            context.executeQueryAsync(onCreateListItemSuccess, onCreateListItemFailed);
        }

        function onCreateListItemSuccess() {
            alert('yay');
        }
        function onCreateListItemFailed(sender, args) {
            alert('failed. ' + args.get_message() + '\n' + args.get_stackTrace());
        }
    </script>