jQuery异步框架探究2:jQuery.Deferred方法

1 内部实现

	Deferred: function( func ) {
		var deferred = jQuery._Deferred(),
			failDeferred = jQuery._Deferred(),
			promise;
		// Add errorDeferred methods, then and promise
		jQuery.extend( deferred, {
			then: function( doneCallbacks, failCallbacks ) {
				deferred.done( doneCallbacks ).fail( failCallbacks );
				return this;
			},
			always: function() {
				return deferred.done.apply( deferred, arguments ).fail.apply( this, arguments );
			},
			fail: failDeferred.done,
			rejectWith: failDeferred.resolveWith,
			reject: failDeferred.resolve,
			isRejected: failDeferred.isResolved,
			pipe: function( fnDone, fnFail ) {
				return jQuery.Deferred(function( newDefer ) {
					jQuery.each( {
						done: [ fnDone, "resolve" ],
						fail: [ fnFail, "reject" ]
					}, 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().then( newDefer.resolve, newDefer.reject );
								} else {
									newDefer[ action ]( 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 ) {
					if ( promise ) {
						return promise;
					}
					promise = obj = {};
				}
				var i = promiseMethods.length;
				while( i-- ) {
					obj[ promiseMethods[i] ] = deferred[ promiseMethods[i] ];
				}
				return obj;
			}
		});
		// Make sure only one callback list will be used
		deferred.done( failDeferred.cancel ).fail( deferred.cancel );
		// Unexpose cancel
		delete deferred.cancel;
		// Call given func if any
		if ( func ) {
			func.call( deferred, deferred );
		}
		return deferred;
	},

2 对jQuery._Deferred()扩展的promise()函数

3 对jQuery._Deferred()扩展的pipe()函数

最后再次郑重申明：本系列文章未经许可，严禁转载。

原文：http://blog.csdn.net/warhin/article/details/50986887