The document discusses jQuery deferred and promise objects. It provides examples of using deferred objects to manage asynchronous operations and callbacks. Key points covered include: - Deferred objects allow registering multiple callbacks and calling callback queues while propagating the state of asynchronous functions. - Deferred objects have three states: pending, resolved, rejected. Their state cannot be changed once set. - The .then(), .done(), .fail(), and .progress() methods allow adding callback functions to deferred objects. - Promise objects are returned from deferred objects and are read-only versions used to observe deferred state without modifying it. - jQuery.when() can execute callback functions when one or more deferred/promise objects are resolved.

1. daiying.zhang
jQuery延迟对象
Deferred Object

2. event

3. so easy…

4. More then one

5. :)
document.getElementById('foo').addEventListener('click', function(){
/* something ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* something else ...*/
});

6. then..
document.getElementById('foo').addEventListener('click', function(){
/* something ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* something else ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* something more ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* something more then more ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* oh my god ! */
});

7. var img = new Image();
img.onload = function(){
//...
alert('load');
}
img.src = "http://localhost/aaa.jpg?t=" + Math.random();
// ...
setTimeout(function(){
alert(img.complete)
img.onload = function(){
// todo something
alert('ok');
}
}, 3000)

8. then..
document.getElementById('foo').addEventListener('click', function(){
/* something ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* something else ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* something more ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* something more then more ...*/
});
document.getElementById('foo').addEventListener('click', function(){
/* oh my god ! */
});

9. async
顺序

10. ?

11. :(

12. ?

13. :)
setTimeout(function(){
/* this may takes a long time*/
var value = foo(65535);
/* call it here */
calc(result);
}, 5000)
//calc(result);

14. then…
step1(1, function(){
step2(2, function(){
setp3(3, function(){
setp4(4, function(){
// Oh my god !
})
})
}
})

15. “Callback hell”

16. 代码变复杂
不利于模块化
可维护性差
紧耦合

17. Ajax

18. $.ajax({
url: 'http://www.xxx.com/api',
type: 'POST',
success: function(json){
/* do something */
},
error: function(msg){
/* get an error */
}
})

19. Exception

20. try{
setTimeout(function(){
throw new Error(':(')
}, 0)
}catch(e){
alert('get an error');
}

21. Promise/A

23. $
jQuery is coming…

24. Deferred / Callbacks

25. Callbacks

26. 1、jQuery 1.7 版本中新增的
2、jQuery.Callbacks() 函数返回的对象
3、对象对管理回调列表提供了强⼤大的⽅方式
4、能够增加、删除、触发、禁⽤用回调函数
5、⽀支持不同的参数来控制回调执⾏行

30. // todo demo

31. Deferred

32. 一个可链式调用的工具对象,管理回调，简化异步操作
可以注册多个回调，调用回调队列，并且传播任何同
步或异步函数的状态
三种状态:pending|resolved|rejected
状态改变后无法再次修改
拥有一个promise对象

33. API

35. var def = jQuery.Deferred();
def.done(function(){ console.warn('done'); });
def.fail(function(){ console.warn('fail'); });
console.warn('def.state() ==>', def.state());
def.reject();
console.warn('def.state() ==>', def.state());
var def = jQuery.Deferred();
def.then(function(){ console.warn('done'); },
function(){ console.warn('fail'); });
console.warn('def.state() ==>', def.state());
def.reject();
console.warn('def.state() ==>', def.state());

36. deferred.then()

37. deferred.then(fnDone[, fnFail[, fnPro]])
分别调用deferred的
.done(), .fail(), .progress()
添加相应回调函数
return this
start
end
version : 1.5.x/1.6.x/1.7.x
创建新Deferred对象
(newDefer)
分别调用deferred的
.done(), .fail(), .progress()
添加相应回调函数
return newDefer.promise()
start
end
version : 1.8.x+
职责：
1、执⾏行回掉函数
2、改变新的Deferred对象的状态
3、返回新的Deferred对象

38. deferred.then/pipe
分别调用deferred的
.done(), .fail(), .progress()
添加相应回调函数
return this
start
end
version : 1.5.x/1.6.x/1.7.x
then
创建新Deferred
对象
(newDefer)
分别调用deferred的
.done(), .fail(), .progress()
添加相应回调函数
return
newDefer.promise()
start
end
version : 1.6.x/1.7.x
pipe
创建新Deferred
对象
(newDefer)
分别调用deferred的
.done(), .fail(), .progress()
添加相应回调函数
return
newDefer.promise()
start
end
version : 1.8.x+
then

40. d1
done function
fail function
state “pending”
… …
doneList Array
failList Array
doneList
0 changeState
1 failList.disable
2 progress.lock
donList和failList实际上不是d1的属性，只是一个局部变量，
为了演示方便，加入到d1

41. d1
done function
fail function
state “pending”
… …
doneList Array
failList Array
doneList
0 changeState
1 failList.disable
2 progress.lock
3 function
doneList
0 changeState
1 doneList.disable
2 progress.lock
d2
done function
fail function
then function
… …
doneList Array
failList Array
f1
f2
f3
failList
0 changeState
1 failList.disable
2 progress.lock

42. d1
done function
then function
state “pending”
… …
doneList Array
failList Array
doneList
0 changeState
1 failList.disable
2 progress.lock
3 function
doneList
0 changeState
1 doneList.disable
2 progress.lock
d2
done function
fail function
then function
… …
doneList Array
failList Array
f1
f2
f3
failList
0 changeState
1 failList.disable
2 progress.lock
start
call fn & get result
(returned)
isPromise
(returned)
end
returned.promise()
.then(…)
newDefer[resolve
With|rejectWith|
progressWith]
Y
N

43. d1
done function
fail function
then function
… …
doneList Array
failList Array
doneList
0 changeState
1 failList.disable
2 progress.lock
3 function
doneList
0 changeState
1 doneList.disable
2 progress.lock
3 function
d2
done function
fail function
then function
… …
doneList Array
failList Array
f1
f2
f3
failList
0 changeState
1 failList.disable
2 progress.lock
3 function

44. d1
done function
then function
state “resolved”
… …
doneList Array
failList Array
doneList
0 changeState
1 failList.disable
2 progress.lock
3 function
doneList
0 changeState
1 doneList.disable
2 progress.lock
3 function
d2
done function
fail function
then function
… …
doneList Array
failList Array
f1
f2
f3
failList
0 changeState
1 failList.disable
2 progress.lock
3 function
isPromise(returned = d) == true
d.then(d2.resolve, d2.reject)
d2.reject()
// TODO ….
:)

45. d1
done function
fail function
then function
… …
doneList Array
failList Array
failList
0 changeState
1 doneList.disable
2 progress.lock
3 undefined
doneList
0 changeState
1 doneList.disable
2 progress.lock
3 function
d2
done function
fail function
then function
… …
doneList Array
failList Array
f1
f2
f3
faiList
0 changeState
1 failList.disable
2 progress.lock
3 function
returned = fnFail && returned
returned == false
d2.rejectWith()
var deferred = $.Deferred();
deferred.then(function(res){
console.warn('ok 1');
},function(err){
console.warn('err 1');
})
.then(function(res){
console.warn('ok 2');
},function(err){
console.warn('err 2');
})
.then(function(res){
console.warn('ok 3');
},function(err){
console.warn('err 3');
});
deferred.reject();
p(deferred)

46. deferred.done/fail/
progress()

48. done() or then() ?

49. 顺序 / 值
// then
var def = $.Deferred();
def.then(
function(val){ console.warn('done +1 ==>', val); return val + 1 }
).then(
function(val){ console.warn('done +2 ==>', val); return val + 2 }
).then(
function(val){ console.warn('done +3 ==>', val); return val + 3 }
)
def.resolve(1)
// done
var def = $.Deferred();
def.done(
function(val){ console.warn('done +1 ==>', val); return val + 1 }
).done(
function(val){ console.warn('done +2 ==>', val); return val + 2 }
).done(
function(val){ console.warn('done +3 ==>', val); return val + 3 }
)
def.resolve(1)
// then async
var def = $.Deferred();
def.then( // d1

50. deferred.promise()

51. 返回一个Deferred的只读对象
var def = $.Deferred();
p(def)

52. Deferred or Promise ?

53. Read Only

54. jQuery.when()

55. 提供一种方法来执行一个或多个对象的回调函数，
Deferred(延迟)对象通常表示异步事件。

57. use
// no-deferred object
var obj = {
a:1,
b:2
}
function func1(obj){
console.warn(obj)
}
function func2(obj){
console.warn(obj)
}
func1(obj);
func2(obj);
// deferred object
// deferred object
var def1 = $.Deferred();
var def2 = $.Deferred();
function func1(obj){
console.warn(obj)
}
function func2(obj){
console.warn(obj)
}

58. Thx
:)