Attempt at an `optionsHash` binding for Knockout.js

optionsHash.js

ko.bindingHandlers.optionsHash = {
    update: function (element, valueAccessor, allBindingsAccessor) {
        var hash = ko.utils.unwrapObservable(valueAccessor());
        var asArray = Object.keys(hash).map(function (k) {
            return {
                key: k,
                val: hash[k]
            };
        });

        function maskedAllBindingsAccessor() {
            return ko.utils.extend(allBindingsAccessor(), { optionsValue: "key", optionsText: "val" });
        }
        function maskedValueAccessor() {
            return asArray;
        }

        return ko.bindingHandlers.options.update(element, maskedValueAccessor, maskedAllBindingsAccessor);
    }
};