how to get id of newest item in the document library

i hvae applied the below code and i got the id of all the item present in the document library.i want to retrive the newest's item id.here is my code.:

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.min.js"></script>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery.SPServices/2014.02/jquery.SPServices-2014.02.min.js"></script>
<script type="text/javascript">
$(document).ready(function () {               
                    ExecuteOrDelayUntilScriptLoaded(GetListItemId, "sp.js");          
});

function GetListItemId() {

        var context = new SP.ClientContext.get_current();
        var web = context.get_web();
        var list = web.get_lists().getByTitle('docLib1');
        var query = SP.CamlQuery.createAllItemsQuery();
        allItems = list.getItems(query);
        context.load(allItems);
        context.executeQueryAsync(Function.createDelegate(this, this.successGetListItemId));
    }

    function successGetListItemId() {
                
        var TextFiled = "";
        var ListEnumerator = this.allItems.getEnumerator();
        while (ListEnumerator.moveNext()) {
            var currentItem = ListEnumerator.get_current();
            TextFiled += currentItem.get_item('ID');
        }
        alert(TextFiled);
    }
</script>
</script>
<input type="button" onclick="GetListItemId()" value="Copy">