node async foreach

gistfile1.js

Array.prototype.forEachAsync = function (callback, complete) {
    var raiseComplete/*: (arg?: bool) => void*/ = complete ? (function (arg) {
        complete(arg);
    }) : (function () { });

    function next (self, index, length) { /* rec */
        if (index === length) {
            raiseComplete(true);
        } else {
            process.nextTick(function () {
                function closureNext () {
                    next(self, index + 1, length);
                }
                var flow = callback(self[index], index, self, closureNext);
                if (flow === false) {
                    raiseComplete(false);
                } else if (flow === true) {
                    return; // closure next
                } else {
                    closureNext();
                }
            });
        }
    }

    next(Object(this), 0, this.length);
};

JavaScript, Y U NO HAVE PATTERN MATCHING