maybe2

var greaterThan = function (num) { return function (x) { return x > num ? x:null; }; };
var lessThan = function (num) { return function (x) { return x < num ? x:null; }; };
var definitelyUndefined;
log('All together: ', maybe(definitelyUndefined)
                        .is(Number)
                        .map(greaterThan(0))
                        .map(lessThan(42))
                        .getOrElse(9000));