自己动手实现 jQuery Callbacks

最近大量的用到jQuery Callbacks 对象，jQuery库中的$.ajax()和$.Deferred() 对象也是基于这个对象实现，中午不困， 利用这点时间片自己动手模拟实现了这个对象的部分功能（没有100%完全测试）， 以加深理解：

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： 

 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）

       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)

  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 

    $.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' } );