Knockout ObservableArray Map. Snippet from: Ryan Niemeyer - Getting the Most Out of Knockout.js @ http://vimeo.com/51103092

knockout-observableArrayMap.js

(function (undefined) {

    //
    // simple map function to extend the observableArray.
    ko.observableArray.fn.map = function (data, Constructor) {
        var mapped = ko.utils.arrayMap(data, function (item) {
            return new Constructor(item);
        });

        this(mapped);
        return this;
    };

})();