deferred

Deferred

/**
 *  @return {Object.<function>}
 */
function Deferred() {
    /*-------------------------------------------
        INIT
    -------------------------------------------*/
    var queue = [];
    
    /*-------------------------------------------
        PUBLIC
    -------------------------------------------*/
    function resolve() {
        var arr = [].concat(queue),
            len = arr.length,
            i = 0;
        
        queue = null;
        for (; i < len; ++i) {
            arr[i]();
        }
    }
    function done(fnc) {
        queue ? queue.push(fnc) : fnc();
    }
    function promise() {
        return {
            done : done
        };
    }
    /*-------------------------------------------
        EXPORT
    -------------------------------------------*/
    return {
        resolve : resolve,
        promise : promise,
        done    : done
    };
}

Deferred2

/**
 *  @return {Object.<function>}
 */
function Deferred() {
    /*-------------------------------------------
        PRIVATE
    -------------------------------------------*/
    var _queue = [],
        _data;
    
    /*-------------------------------------------
        PUBLIC
    -------------------------------------------*/
    /**
     *  @return {boolean}
     */
    function isResolved() {
        return !_queue;
    }
    /**
     *  @param  {*} data
     *  @return {undefined}
     */
    function resolve(data) {
        if (isResolved()) {
            return;
        }
        
        var arr = _queue,
            len = arr.length,
            i   = 0;
        
        _queue = null;
        _data  = data;
        for (; i < len; ++i) {
            arr[i](data);
        }
    }
    /**
     *  @param  {function} func
     *  @return {undefined}
     */
    function done(func) {
        _queue ? _queue.push(func) : func(_data);
    }
    /*-------------------------------------------
        EXPORT
    -------------------------------------------*/
    return {
        isResolved : isResolved,
        resolve    : resolve,
        done       : done
    };
}

DeferredQueue

/**
 *  @return {Object.<function>}
 */
function DeferredQueue() {
    /*-------------------------------------------
        INIT
    -------------------------------------------*/
    var queue   = [],
        isReady = 1;
    
    /*-------------------------------------------
        PRIVATE
    -------------------------------------------*/
    function exec() {
        var arr = queue,
            len = arr.length,
            fnc;
        
        isReady = !len;
        if (len) {
            fnc = queue.shift();
            fnc().done(exec);
        }
    }
    /*-------------------------------------------
        PUBLIC
    -------------------------------------------*/
    function done(fnc) {
        var arr = queue;
        
        arr.push(fnc);
        if (isReady) {
            exec();
        }
    }
    /*-------------------------------------------
        EXPORT
    -------------------------------------------*/
    return {
        done : done
    };
}

pipe

//////////////////////////////////////////////////

/**
 *  @param {function:Deferred} fnc
 *  @return {Object.<function>}
 */
function pipe(fnc) {
    /**
     *  @param {Deferred} dfd
     *  @return {function}
     */
    function createPipe(dfd1) {
        /**
         *  @param {function:Deferred} fnc
         *  @return {Object.<function>}
         */
        return function(fnc) {
            var dfd3 = new Deferred;
            
            dfd1 && dfd1.done && dfd1.done(function(data) {
                var dfd2 = fnc(data);
                
                dfd2 && dfd2.done && dfd2.done(function(data) {
                    dfd3.resolve(data);
                });
            });
            return {
                pipe : createPipe(dfd3)
            };
        };
    }
    return {
        pipe : createPipe(fnc())
    };
}

when

/**
 * @param {Array.<Deferred>} arr
 * @return {Deferred}
 */
function when(arr) {
    var dfd = new Deferred,
        len = arr.length,
        i   = len;
    
    while (i--) {
        arr[i].done(handleDone);
    }
    
    function handleDone() {
        --len || dfd.resolve();
    }
    return dfd;
}