Data to be sent to the server. It is appended to the url for GET requests, and converted to a JSON string for other requests.

The HTTP method to use for the request (e.g. "POST", "GET", "PUT"). The default is "GET".

A JavaScript object containing key/value pairs to be added to the request headers.

Function to be called if the request succeeds. The function has a single parameter of type XMLHttpRequest that represents the request.

The number of milliseconds the request can take before automatically being terminated. The default value is 0, which means there is no timeout.