async queue

queue.js

/** 
example:
function async(n, callback) {
    setTimeout(function() {
        callback(n);
    }, n);
}

queue([100, 200], async, function(err, r) {console.log(r);}); // => [100, 200]
**/

function queue(arr, iterator, ignoreErr, callback) {
    var aLen = arguments.length;
    var result = [];
    var len = arr.length;
    var i = 0;

    if(aLen < 3) throw Error('callback required');

    if(aLen === 3) {
        callback = ignoreErr;
        ignoreErr = false;
    }

    function next() {
        if(i < len) {
            iterator(arr[i], function(err, r) {
                if(err && !ignoreErr) {
                    callback(err, result);
                } else {
                    result[i++] = r;
                    next();
                }
            });
        } else {
            callback(null, result);
        }
    };

    next();
};