How can you prevent unintended side effects from callbacks?

Mar 12, 2014 ... Defining an Error-First Callback · The first argument of the callback is reserved for an error object. If an error occurred, it will be returned ... Sep 5, 2023 ... So the beginning and end of the function are reached. However, I see neither “ERROR” nor “SUCCESS” in the log, so the callback seems not to be ... A pre-request callback function that can be used to modify the jqXHR (in jQuery 1.4.x, XMLHTTPRequest) object before it is sent. Use this to set custom headers, ... Mar 4, 2023 ...