jQuery Deferred(http://www.ruanyifeng.com/blog/2011/08/a_detailed_explanation_of_jquery_deferred

jQuery Deferred(http://www.ruanyifeng.com/blog/2011/08/a_detailed_explanation_of_jquery_deferred_object.html)



<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>$.when</title>
    <script src="http://the5fireblog.b0.upaiyun.com/staticfile/jquery-1.10.2.js"></script>
    <script>
        function fn1(){
            setTimeout(alert("fn1"),5000);
        }
        $.when(fn1()).done(function(){
            alert("fn1执行完毕！")
        }).fail(function(){
            alert("出错了！")
        })
    </script>
</head>
<body>

</body>
</html>

但是，这样写的话，done()方法会立即执行，起不到回调函数的作用。原因在于$.when()的参数只能是deferred对象，所以必须对wait()进行改写：

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>$.when</title>
    <script src="http://the5fireblog.b0.upaiyun.com/staticfile/jquery-1.10.2.js"></script>
    <script>
        /*function fn1(){
            setTimeout(alert("fn1"),5000);
        }
        $.when(fn1()).done(function(){
            alert("fn1执行完毕！")
        }).fail(function(){
            alert("出错了！")
        })*/
        var dtd = $.Deferred();//新建一个Deferred对象
        var wait = function(dtd){
            var test = function(){
                alert("test执行完毕！");
//                dtd.resolve();//改变deferred对象的状态
                dtd.reject();
            }
            setTimeout(test, 5000);
            return dtd;
        }
        $.when(wait(dtd)).done(function(){
            alert("成功！")
        }).fail(function(){
            alert("失败！")
        })
    </script>
</head>
<body>

</body>
</html>

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>$.when</title>
    <script src="http://the5fireblog.b0.upaiyun.com/staticfile/jquery-1.10.2.js"></script>
    <script>
        var wait = function(){
            var dtd = $.Deferred();//新建一个Deferred对象
            var test = function(){
                alert("test执行完毕！");
                dtd.resolve();//改变deferred对象的状态
//                dtd.reject();
            }
            setTimeout(test, 2000);
            return dtd.promise();//返回promise对象
        }
//        var d = wait(dtd);//新建一个d对象，以为对这个对象进行操作
        $.when(wait()).done(function(){
            alert("成功！")
        }).fail(function(){
            alert("失败！")
        })
//        dtd.resolve();
//        d.resolve();//promise对象不能resolve,这个语句无效
    </script>
</head>
<body>

</body>
</html>

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>$.when</title>
    <script src="http://the5fireblog.b0.upaiyun.com/staticfile/jquery-1.10.2.js"></script>
    <script>
        var wait = function(){
            var test = function(){
                alert("test执行完毕！");
            }
            setTimeout(test, 2000);
        }
        $.Deferred(wait).done(function(){
            alert("成功！")
        }).fail(function(){
            alert("失败！")
        })
    </script>
</head>
<body>

</body>
</html>