CODE EXAMPLE FOR JAVASCRIPT

sharepoint javascript get last added item

function CreateListItemWithDetails(listName, newItemBody) {

    var item = newItemBody;
    return $.ajax({
        url: _spPageContextInfo.siteAbsoluteUrl + "/_api/web/lists/getbytitle('" + listName + "')/items",
        type: "POST",
        contentType: "application/json;odata=verbose",
        data: JSON.stringify(item),
        headers: {
            "Accept": "application/json;odata=verbose",
            "X-RequestDigest": $("#__REQUESTDIGEST").val(),
            "content-Type": "application/json;odata=verbose"
        }

    });
}

CreateListItemWithDetails(listName, newItemBody)
    .then(function(data){
        //success callback
        var NewlyCreatedItemId = data.d.ID;
    }, function(data){
        //failure callback
    });