Question

The Deferred object documentation says it can take an optional function argument, but there is not an example. How do I use this?

Answer 1

It is a syntactic sugar, through which you can add a callback/handler on resolve or reject on the same deferred object.

so, the following two code pieces will do the same thing.

// with constructor method argument
var x = $.Deferred(function(selfDfd){ 
           selfDfd.done( console.log.bind(console,'I am resolved,in constructor')); 
        });
x.resolve();

// without constructor method argument

var y = $.Deferred();
y.done(console.log.bind(console,'I am resolved, NO constructor args'))
y.resolve();