jq中Deferred对象的使用

    var d=$.Deferred();
    //deferred下面的方法有:
    // ["resolve", "resolveWith", "reject", "rejectWith", "notify", "notifyWith",
    // "state", "always", "then", "promise", "pipe", "done", "fail", "progress"]
    console.info(Object.keys(d));
    console.info(d.pipe== d.then);//true
    console.info(d.state());//初始化pending状态

    //------------resolve对应的是done------------
    function fn1(){
        var def= $.Deferred();
        setTimeout(function(){
            def.resolve('成功了!');
        },1000);
        return def.promise();
    }
    fn1().done(function(data){
        console.info(data);//成功了!
    });
    //或者可以这样写
    fn1().then(function(data){ //then的参数为( fnDone, fnFail, fnProgress)
        console.info(data);//成功了!
    });

    //------------reject对应的是fail------------
    function fn2(){
        var def= $.Deferred();
        setTimeout(function(){
            def.reject('失败了!');
        },1000);
        return def.promise();
    }
    fn2().fail(function(data){
        console.info(data);//失败了!
    });
    //或者可以这样写
    fn2().then(function(data){ //then的参数为( fnDone, fnFail, fnProgress)
        //不会走
    },function(data){
        console.info(data);
    });

    //------------notify对应的是progress------------
    function fn3(){
        var def= $.Deferred();
        setTimeout(function(){
            def.notify('传递给下一步回调的通知!');
        },1000);
        return def.promise();
    }
    fn3().progress(function(data){
        console.info(data);//传递给下一步回调的通知!
    });
    //或者可以这样写
    fn3().then(function(data){ //then的参数为( fnDone, fnFail, fnProgress)
        //不会走
    },function(data){
        //不会走
    },function(data){
        console.info(data);//传递给下一步回调的通知!
    });

    //------------always 不管成功与否都会执行回调------------
    //deferred.done( arguments ).fail( arguments );
    function fn4(){
        var def= $.Deferred();
        setTimeout(function(){
            Math.random()>0.5?def.resolve('成功!'): def.reject('失败!')
        },1000);
        return def.promise();
    }
    fn4().always(function(data){
        console.info(data);//成功!or失败!
    });

    //------------连续的回调依次执行------------
    /*第一异步程序*/
    function delayFn1(arg1){
        var def= $.Deferred();
        setTimeout(function(){
            var data=arg1+1;
            console.info("第一步--->",data);
            def.resolve(data);
        },1000);
        return def.promise();
    }
    /*第二个异步程序*/
    function delayFn2(arg2){
        var def= $.Deferred();
        setTimeout(function(){
            var data=arg2+1;
            def.resolve(data);
        },1000);
        return def.promise();
    }
    /*第三个异步程序*/
    function delayFn3(arg3){
        var def= $.Deferred();
        setTimeout(function(){
            var data=arg3+1;
            def.resolve(data);
        },1000);
        return def.promise();
    }

    delayFn1(1).then(function(data){
        console.info("第二步--->",data);
        return delayFn2(data)
    }).then(function(data){
        console.info("第三步--->",data);
        return delayFn3(data)
    }).then(function(data){
        console.info("第四步--->",data);
        alert(data);
    })