Function _filter

public/javascripts/async.js:404–420

(eachfn, arr, iterator, callback)

    };

    function _filter(eachfn, arr, iterator, callback) {
        var results = [];
        eachfn(arr, function (x, index, callback) {
            iterator(x, function (v) {
                if (v) {
                    results.push({index: index, value: x});
                }
                callback();
            });
        }, function () {
            callback(_map(results.sort(function (a, b) {
                return a.index - b.index;
            }), function (x) {
                return x.value;
            }));
        });
    }

    async.select =
    async.filter = doParallel(_filter);