Most web browsers support ajax requests in two modes: Synchronous and Asynchronous. This mode is specified with a boolean bAsync parameter.

var bAsync = false; // Synchronous
request.open(instance.method, instance.url, bAsync);

However, to work with browsers that do not support the Synchronous requests, bAsync is always set to true (Ajax request will always be asynchronous).

// Asynchronous request
request.open(instance.method, instance.url, true);