jquery/src/deferred.js

(function( jQuery ) {

var // Static reference to slice
	sliceDeferred = [].slice;

jQuery.extend({

	Deferred: function( func ) {
		var doneList = jQuery.Callbacks( "once memory" ),
			failList = jQuery.Callbacks( "once memory" ),
			progressList = jQuery.Callbacks( "memory" ),
			state = "pending",
			lists = {
				resolve: doneList,
				reject: failList,
				notify: progressList
			},
			promise = {
				done: doneList.add,
				fail: failList.add,
				progress: progressList.add,

				state: function() {
					return state;
				},

				// Deprecated
				isResolved: doneList.fired,
				isRejected: failList.fired,

				always: function() {
					deferred.done.apply( deferred, arguments ).fail.apply( deferred, arguments );
					return this;
				},
				then: function( fnDone, fnFail, fnProgress ) {
					return jQuery.Deferred(function( newDefer ) {
						jQuery.each( {
							done: [ fnDone, "resolve" ],
							fail: [ fnFail, "reject" ],
							progress: [ fnProgress, "notify" ]
						}, function( handler, data ) {
							var fn = data[ 0 ],
								action = data[ 1 ],
								returned;
							if ( jQuery.isFunction( fn ) ) {
								deferred[ handler ](function() {
									returned = fn.apply( this, arguments );
									if ( returned && jQuery.isFunction( returned.promise ) ) {
										returned.promise().done( newDefer.resolve ).fail( newDefer.reject ).progress( newDefer.notify );
									} else {
										newDefer[ action + "With" ]( this === deferred ? newDefer : this, [ returned ] );
									}
								});
							} else {
								deferred[ handler ]( newDefer[ action ] );
							}
						});
					}).promise();
				},
				// Get a promise for this deferred
				// If obj is provided, the promise aspect is added to the object
				promise: function( obj ) {
					if ( obj == null ) {
						obj = promise;
					} else {
						for ( var key in promise ) {
							obj[ key ] = promise[ key ];
						}
					}
					return obj;
				}
			},
			deferred,
			key;

		// Keep pipe for back-compat
		promise.pipe = promise.then;

		// Construct deferred
		deferred = promise.promise({});

		for ( key in lists ) {
			deferred[ key ] = lists[ key ].fire;
			deferred[ key + "With" ] = lists[ key ].fireWith;
		}

		// Handle state
		deferred.done( function() {
			state = "resolved";
		}, failList.disable, progressList.lock ).fail( function() {
			state = "rejected";
		}, doneList.disable, progressList.lock );

		// Call given func if any
		if ( func ) {
			func.call( deferred, deferred );
		}

		// All done!
		return deferred;
	},

	// Deferred helper
	when: function( firstParam ) {
		var args = sliceDeferred.call( arguments ),
			i = 0,
			length = args.length,
			pValues = new Array( length ),
			count = length,
			pCount = length,
			deferred = length <= 1 && firstParam && jQuery.isFunction( firstParam.promise ) ?
				firstParam :
				jQuery.Deferred(),
			promise = deferred.promise();
		function resolveFunc( i ) {
			return function( value ) {
				args[ i ] = arguments.length > 1 ? sliceDeferred.call( arguments ) : value;
				if ( !( --count ) ) {
					deferred.resolveWith( deferred, args );
				}
			};
		}
		function progressFunc( i ) {
			return function( value ) {
				pValues[ i ] = arguments.length > 1 ? sliceDeferred.call( arguments ) : value;
				deferred.notifyWith( promise, pValues );
			};
		}
		if ( length > 1 ) {
			for ( ; i < length; i++ ) {
				if ( args[ i ] && args[ i ].promise && jQuery.isFunction( args[ i ].promise ) ) {
					args[ i ].promise().done( resolveFunc(i) ).fail( deferred.reject ).progress( progressFunc(i) );
				} else {
					--count;
				}
			}
			if ( !count ) {
				deferred.resolveWith( deferred, args );
			}
		} else if ( deferred !== firstParam ) {
			deferred.resolveWith( deferred, length ? [ firstParam ] : [] );
		}
		return promise;
	}
});

})( jQuery );