Error:Input string was not in a correct format. (Javascript)

I'm using SharePoint 2013 online and trying to save a item to a folder content type in a document libary I think the code is nearly rigth but i am getting this error when i hit save button have anyone else had this problem?

Failed Error:Input string was not in a correct format.

Error on this line.

appContext.executeQueryAsync(function () {

This is my function ctName is global.

ctName = 'IFUSimon';
function createListItem() {

console.log("1");
if (itemId == 'null') {

    var listCreationInformation = new SP.ListItemCreationInformation();
    listCreationInformation.set_underlyingObjectType(SP.FileSystemObjectType.folder);
    var folderName = $('#Title').val();
    if (folderName != "") {
        listCreationInformation.set_leafName(folderName);
    } else {
        alert('No title');
        return false;
    }
    listItem = list.addItem(listCreationInformation);
    console.log("3");
    var listContentTypes = list.get_contentTypes();
    console.log("4");
    appContext.load(listContentTypes);
    console.log("5");
    appContext.executeQueryAsync(function () {
        console.log("6");
        var ct;
        console.log("7");
        var ct_enumerator = listContentTypes.getEnumerator();
        console.log("8");
        while (ct_enumerator.moveNext()) {
            ct = ct_enumerator.get_current();
            if (ct.get_name() == ctName) {
                CTID = ct.get_id();
            }
        }
        listItem.set_item('ContentTypeId', CTID);

        console.log("kmr du hitsnart");
        setItems();
        console.log("kmr du hitsnartklarrrr");
    }, fail);  
}
else {

    listItem = item;
    console.log("2");
    setItems();
}
}

Log from chrome console

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Failed Error:Input string was not in a correct format.