jQuery Deferred 回调 最简 教程

Deferrd是jQuery提供的回调方法包装类。

以下内容摘自jQuery Api 1.7

function asyncEvent() {
    var dfd = new jQuery.Deferred();

    // Resolve after a random interval
    setTimeout(function () {
        dfd.resolve("hurray"); //触发成功事件 | 被done注册的函数
    }, Math.floor(400 + Math.random() * 2000));

    // Reject after a random interval
    setTimeout(function () {
        dfd.reject("sorry"); //触发失败事件 | 被fail注册的函数
    }, Math.floor(400 + Math.random() * 2000));

    // Show a "working..." message every half-second
    setTimeout(function working() {
        if (dfd.state() === "pending") {
            dfd.notify("working... "); //触发progress事件
            setTimeout(working, 500);
        }
    }, 1);//精彩的代码
    // Return the Promise so caller can't change the Deferred
    return dfd.promise(); //删掉用于触发的方法：reject,resolve,notify
}

asyncEvent().done(function () {
    console.log('成功');
}).fail(function () {
    console.log('失败');
}).always(function () {
    console.log('不管成败，反正是结束了');
}).progress(function () {
    console.log('you got a message~');
});

还有一些方便使用的函数：$.when（dfd1,[dfd2,[dfd3]]),他返回的还是Deferrd对象。当传入的所有dfd都成功后，才会触发done事件。当任意一个dfd失败，立即触发fail

var a=$.Deferred();
var b=$.Deferred();

$.when(a,b)
.fail(function(){console.log('失败');})
.done(function(){console.log('成功');});

b.resolve()
a.resolve()
//输出：成功

var a=$.Deferred();
var b=$.Deferred();

$.when(a,b)
.fail(function(){console.log('失败');})
.done(function(){console.log('成功');});

b.reject()
//输出：失败

then是一个快捷方法：dfd.then(doneCallback,failCallback,[progressCallback]);

还有：在所有的触发用方法都可以传递一个参数

// Attach a done, fail, and progress handler for the asyncEvent
$.when(asyncEvent()).then(function (status) { //注册成功回调，done
    console.log(status + ', things are going well');
}, function (status) { //注册失败回调,fail
    console.log(status + ', you fail this time');
}, function (status) { //注册progress回调。1.7新增
    $("body").append(status);
});

最后说精彩的代码：http://p2world.iteye.com/blog/1405227

http://p2world.iteye.com/blog/1405238