Javascript 如何使用 jQuery 延迟

jQuery1.5带来了新的延迟对象和附带的方法.when、.Deferred和._Deferred.

对于那些以前没有使用过.Deferred的人，我已经对source for it进行了注释.

这些新方法的可能用途是什么？我们如何着手将它们融入模式？

我已经读过API和source，所以我知道它的作用.我的问题是，我们如何在日常代码中使用这些新功能？

我有一个简单的example个缓冲区类，它按顺序调用Ajax请求.(下一个在前一个结束后开始).

/* Class: Buffer
 *  methods: append
 *
 *  Constructor: takes a function which will be the task handler to be called
 *
 *  .append appends a task to the buffer. Buffer will only call a task when the 
 *  previous task has finished
 */
var Buffer = function(handler) {
    var tasks = [];
    // empty resolved deferred object
    var deferred = $.when();

    // handle the next object
    function handleNextTask() {
        // if the current deferred task has resolved and there are more tasks
        if (deferred.isResolved() && tasks.length > 0) {
            // grab a task
            var task = tasks.shift();
            // set the deferred to be deferred returned from the handler
            deferred = handler(task);
            // if its not a deferred object then set it to be an empty deferred object
            if (!(deferred && deferred.promise)) {
                deferred = $.when();
            }
            // if we have tasks left then handle the next one when the current one 
            // is done.
            if (tasks.length > 0) {
                deferred.done(handleNextTask);
            }
        }
    }

    // appends a task.
    this.append = function(task) {
        // add to the array
        tasks.push(task);
        // handle the next task
        handleNextTask();
    };
};

我正在寻找.Deferred和.when的演示和可能的用法.

看到._Deferred个这样的例子也会很高兴.

例如，链接到新的jQuery.ajax源代码就是作弊.

我特别感兴趣的是，当我们抽象出一个操作是同步还是异步完成时，有哪些技术可用.