keyFilter behavior for knockout.js

ko.bindingHandlers.keyFilter = {

    init: function(element, value, allBindings) {
        var filter = ko.bindingHandlers.keyFilter[allBindings.keyFilter];
        if (!filter) return;

        $(element).keypress(function(event) {
            if (!filter(event.which)) {
                event.stopPropagation();
                return false;
            }
        });
    },

    isDigit: function(keycode) {
        var zero = 48;
        var nine = 57;
        return zero <= keycode && keycode <= nine;
    }

};

// usage
// <input type="text" data-bind="value: someIntegerValue, keyFilter: 'isDigit'"/>