分享Node.js简单的异步操作管理器

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   mysql.query('xxxx').on('success', function(){
        mysql.query('xxxx').on('success', function(){
            mysql.query('xxxx').on('success', function(){
                mysql.query('xxxx').on('success', function(){
                    mysql.query('xxxx').on('success', function(){
                        //let's say fuck
                    });
                });
            });
        });
    });
});

/*
 *  异步管理器
 *  author : jser.me
 *
 *  使用方法：
 *     var asyncMg = require('./AsyncManager');
 *     asyncMg
 *     .push(function( next ){
 *         some_aysnc_method().on('success'{
 *            ....
 *            next();
 *         })
 *     })
 *     .push(function( next ){
 *         other_aysnc_method().on('success'{
 *            ....
 *            next();
 *         })
 *     })
 *     .push( ... )
 *     .run() //执行
 *     .on('success', function(){
 *          allThings_is_down();
 *     });
 *
 *     push方法接受数组
 */
function typeOf( obj ){
    return Object.prototype.toString.call( obj ).match(/\[object ([^\]]*)\]/)[1];
}
function AsyncManager( arg ){
    this.execArrys = [];
    this.push( arg );
}
//使用系统带的继承方法
require('util').inherits( AsyncManager, require('events').EventEmitter );
//标记成功运行的函数数目
AsyncManager.prototype.succCount = 0;

//加入
AsyncManager.prototype.push = function( arg ) {
        var This = this;
        if( typeOf(arg) == 'Array' ){
            arg.forEach( function(v,i){
               This.execArrys.push( v );
            });
        } else {
               This.execArrys.push( arg );
        }
        return this; //链一个
};
//执行
AsyncManager.prototype.run = function(){
        var self = this;
        if( this.succCount == this.execArrys.length ) {
            //所有函数成功执行后触发事件
            this.emit( 'success' );
        } else {
            this.execArrys[ this.succCount ]( self.run.bind( self ) );
        }
        this.succCount++;
        return this; //链一个
};
exports = module.exports = function( arg ){
    return new AsyncManager( arg );
}