jQuery.Deferred()

A factory function that returns a chainable utility object with methods to register multiple callbacks into callback queues, invoke callback queues, and relay the success or failure state of any synchronous or asynchronous function.

jQuery.when()

Provides a way to execute callback functions based on zero or more Thenable objects, usually Deferred objects that represent asynchronous events.

.is()

Check the current matched set of elements against a selector, element, or jQuery object and return true if at least one of these elements matches the given arguments.