Use callbacks.add() to add new callbacks to a callback list:

// A sample logging function to be added to a callbacks list
var foo = function( value ) {
  console.log( "foo: " + value );
};
 
// Another function to also be added to the list
var bar = function( value ) {
  console.log( "bar: " + value );
};
 
var callbacks = $.Callbacks();
 
// Add the function "foo" to the list
callbacks.add( foo );
 
// Fire the items on the list
callbacks.fire( "hello" );
// Outputs: "foo: hello"
 
// Add the function "bar" to the list
callbacks.add( bar );
 
// Fire the items on the list again
callbacks.fire( "world" );
 
// Outputs:
// "foo: world"
// "bar: world"