Creates an instance of XmlHttpRequestConnection object This connection class handles low-level implementation of XHR connection for generic (non-Microsoft) browsers
Basic request implemented via XHR technique
structure containing all needed params and data
a set of callbacks to apply on a specific XHR event like onload, onerror, onprogress, etc.
function, which will be executed on request success
Connection checks itself for compatibility with running environment
whether the connection is compatible with current environment