用法和$.Callbacks完全一致 ， 但是只是实现了add , remove , fire , empty, has和带参数的构造函数功能， $.Callbacks 还有disable,disabled, fireWith , fired , lock, locked 方法

代码如下：

复制代码 代码如下:
String.prototype.trim = function ()
{
return this.replace( /^\s+|\s+$/g, '' );
};

// Simulate jQuery.Callbacks object
function MyCallbacks( options )
{
var ops = { once: false, memory: false, unique: false, stopOnFalse: false };

if ( typeof options === 'string' && options.trim() !== '' )
{
var opsArray = options.split( /\s+/ );
for ( var i = 0; i < options.length; i++ )
{
if ( opsArray[i] === 'once' )
ops.once = true;
else if ( opsArray[i] === 'memory' )
ops.memory = true;
else if ( opsArray[i] === 'unique' )
ops.unique = true;
else if ( opsArray[i] === 'stopOnFalse' )
ops.stopOnFalse = true;
}
}

var ar = [];
var lastArgs = null;
var firedTimes = 0;

function hasName( name )
{
var h = false;

if ( typeof name === 'string'
&& name !== null
&& name.trim() !== ''
&& ar.length > 0 )
{
for ( var i = 0; i < ar.length; i++ )
{
if ( ar[i].name === name )
{
h = true;
break;
}
}
}

return h;
}

// add a function
this.add = function ( fn )
{
if ( typeof fn === 'function' )
{
if ( ops.unique )
{
// check whether it had been added before
if ( fn.name !== '' && hasName( fn.name ) )
{
return this;
}
}

ar.push( fn );

if ( ops.memory )
{
// after added , call it immediately
fn.call( this, lastArgs );
}
}

return this;
};

// remove a function
this.remove = function ( fn )
{
if ( typeof ( fn ) === 'function'
&& fn.name !== ''
&& ar.length > 0 )
{
for ( var i = 0; i < ar.length; i++ )
{
if ( ar[i].name === fn.name )
{
ar.splice( i, 1 );
}
}
}

return this;
};

// remove all functions
this.empty = function ()
{
ar.length = 0;
return this;
};

// check whether it includes a specific function
this.has = function ( fn )
{
var f = false;

if ( typeof ( fn ) === 'function'
&& fn.name !== ''
&& ar.length > 0 )
{
for ( var i = 0; i < ar.length; i++ )
{
if ( ar[i].name === fn.name )
{
f = true;
break;
}
}
}

return f;
};

// invoke funtions it includes one by one
this.fire = function ( args )
{
if ( ops.once && firedTimes > 0 )
{
return this;
}

if ( ar.length > 0 )
{
var r;

for ( var i = 0; i < ar.length; i++ )
{
r = ar[i].call( this, args );

if ( ops.stopOnFalse && r === false )
{
break;
}
}
}

firedTimes++;

if ( ops.memory )
{
lastArgs = args;
}

return this;
};
};

测试函数如下：（注意fn1 fn2是匿名函数， fn2返回false , fn3是有“名”函数）

复制代码 代码如下:
var fn1 = function ( v )
{
console.log( 'fn1 ' + ( v || '' ) );
};

var fn2 = function ( v )
{
console.log( 'fn2 ' + ( v || '' ) );
return false;
};

function fn3( v )
{
console.log( 'fn3 ' + ( v || '' ) );
};

1 . 测试add & fire

var cb=new MyCallbacks();

cb.add(fn1)

cb.add(fn2)

cb.add(fn3)

cb.fire('hello')

输出：

fn1 hello
fn2 hello
fn3 hello

2.测试remove
var cb=new MyCallbacks();

cb.add(fn1)

cb.add(fn2)

cb.add(fn3)

cb.remove(fn1)
cb.fire('hello')
cb.remove(fn3)
cb.fire('hello')
输出：

fn1 hello
fn2 hello
fn3 hello
----------------------------
fn1 hello
fn2 hello

2.测试has
var cb=new MyCallbacks();

cb.add(fn1)

cb.add(fn2)

cb.add(fn3)

cb.has(fn1)

cb.has(fn3)

输出：

false

---------------

true

3.测试带参数的构造函数 : once

var cb=new MyCallbacks('once')

cb.add(fn1)

cb.fire('hello')

cb.fire('hello')

cb.add(fn2)

cb.fire('hello')

输出：

hello

-------------------

------------------

------------------------------

4.测试带参数的构造函数 : memory

var cb=new MyCallbacks('memory')

cb.add(fn1)

cb.fire('hello') // 输出 : fn1 hello

cb.add(fn2) // 输出 : fn2 hello

cb.fire('hello')

输出 :

fn1 hello

fn2 hello

5.测试带参数的构造函数 : stopOnFalse

var cb=new MyCallbacks('stopOnFalse')

cb.add(fn1)

cb.add(fn2)

cb.add(fn3)

cb.fire('hello')

输出：

fn1 hello
fn2 hello
6.测试带参数的构造函数 :unique

var cb=new MyCallbacks('unique')

b.add(fn3)

b.add(fn3)

cb.fire('hello')

输出：

fn3 hello

7. 测试带组合参数的构造函数：四个设置参数可以随意组合，一下只测试全部组合的情况， 不然要写16个测试用例 T_T

var cb=new MyCallbacks('once memory unique stopOnFalse')

cb.add(fn1) // 输出： fn1

cb.add(fn2) // 输出： fn2

cb.add(fn3) // 输出： fn3

cb.fire('hello')

输出：

fn1 hello
fn2 hello
cb.fire('hello') // 输出：没有输出

以下是官方API 文档：

Description: A multi-purpose callbacks list object that provides a powerful way to manage callback lists.The $.Callbacks() function is internally used to provide the base functionality behind the jQuery $.ajax() and$.Deferred() components. It can be used as a similar base to define functionality for new components.

构造函数 ： jQuery.Callbacks( flags )

flags
Type: String
An optional list of space-separated flags that change how the callback list behaves.
Possible flags:
once: Ensures the callback list can only be fired once (like a Deferred).
memory: Keeps track of previous values and will call any callback added after the list has been fired right away with the latest "memorized" values (like a Deferred).
unique: Ensures a callback can only be added once (so there are no duplicates in the list).
stopOnFalse: Interrupts callings when a callback returns false.
By default a callback list will act like an event callback list and can be "fired" multiple times.

Two specific methods were being used above: .add() and .fire(). The .add() method supports adding new callbacks to the callback list, while the .fire() method executes the added functions and provides a way to pass arguments to be processed by the callbacks in the same list.

利用Callbacks 实现发布订阅模式 pub/sub: (官方文档)

复制代码 代码如下:
var topics = {};

jQuery.Topic = function ( id )
{
var callbacks,
method,
topic = id && topics[id];

if ( !topic )
{
callbacks = jQuery.Callbacks();
topic = {
publish: callbacks.fire,
subscribe: callbacks.add,
unsubscribe: callbacks.remove
};
if ( id )
{
topics[id] = topic;
}
}
return topic;
};

使用

复制代码 代码如下:
$.Topic( 'mailArrived' ).subscribe( function ( e )
{
console.log( 'Your have new email! ' );
console.log( "mail title : " + e.title );
console.log( "mail content : " + e.content );
}
);

$.Topic( 'mailArrived' ).publish( { title: 'mail title', content: 'mail content' } );

实现了其余的全部功能 ：callbacks.disable , callbacks.disabled, callbacks.fired,callbacks.fireWith, callbacks.lock, callbacks.locked ,然后重构了下代码结构， 将实现放入了匿名函数内， 然后通过工厂方法 window.callbacks 返回实例，以免每次使用必须 new .

具体代码如下， 有兴趣和时间的可以对照jQuery版本的Callbacks对比下 ：

复制代码 代码如下:
( function ( window, undefined )
{
// Simulate jQuery.Callbacks object
function Callbacks( options )
{
var ops = { once: false, memory: false, unique: false, stopOnFalse: false },
ar = [],
lastArgs = null,
firedTimes = 0,
_disabled = false,
_locked = false;

if ( typeof options === 'string' && options.trim() !== '' )
{
var opsArray = options.split( /\s+/ );
for ( var i = 0; i < options.length; i++ )
{
if ( opsArray[i] === 'once' )
ops.once = true;
else if ( opsArray[i] === 'memory' )
ops.memory = true;
else if ( opsArray[i] === 'unique' )
ops.unique = true;
else if ( opsArray[i] === 'stopOnFalse' )
ops.stopOnFalse = true;
}
}

function hasName( name )
{
var h = false;

if ( typeof name === 'string'
&& name !== null
&& name.trim() !== ''
&& ar.length > 0 )
{
for ( var i = 0; i < ar.length; i++ )
{
if ( ar[i].name === name )
{
h = true;
break;
}
}
}

return h;
}

// add a function
this.add = function ( fn )
{
if ( typeof fn === 'function' )
{
if ( ops.unique )
{
// check whether it had been added before
if ( fn.name !== '' && hasName( fn.name ) )
{
return this;
}
}

ar.push( fn );

if ( ops.memory )
{
// after added , call it immediately
fn.call( this, lastArgs );
}
}

return this;
};

// remove a function
this.remove = function ( fn )
{
if ( typeof ( fn ) === 'function'
&& fn.name !== ''
&& ar.length > 0 )
{
for ( var i = 0; i < ar.length; i++ )
{
if ( ar[i].name === fn.name )
{
ar.splice( i, 1 );
}
}
}

return this;
};

// remove all functions
this.empty = function ()
{
ar.length = 0;
return this;
};

// check whether it includes a specific function
this.has = function ( fn )
{
var f = false;

if ( typeof ( fn ) === 'function'
&& fn.name !== ''
&& ar.length > 0 )
{
for ( var i = 0; i < ar.length; i++ )
{
if ( ar[i].name === fn.name )
{
f = true;
break;
}
}
}

return f;
};

this.disable = function ()
{
_disabled = true;
return this;
};

this.disabled = function ()
{
return _disabled;
};

this.fired = function ()
{
return firedTimes > 0;
};

function _fire( context, args )
{
if ( _disabled || ops.once && firedTimes > 0 || _locked )
{
return;
}

if ( ar.length > 0 )
{
var r;

for ( var i = 0; i < ar.length; i++ )
{
r = ar[i].call( context, args );

if ( ops.stopOnFalse && r === false )
{
break;
}
}
}

firedTimes++;

if ( ops.memory )
{
lastArgs = args;
}

};

this.fireWith = function ( context, args )
{
context = context || this;
_fire( context, args );
return this;
};

this.fire = function ( args )
{
_fire( this, args );
return this;
};

this.lock = function ()
{
_locked = true;
return this;
};

this.locked = function ()
{
return _locked;
};

};

// exposed to global as a factory method
window.callbacks = function ( options )
{
return new Callbacks( options );
};

} )( window );