ko.bindingHandler.format.js

    // overrwrite the built in text binding handler to allow for formatting
    var origTextHandler = ko.bindingHandlers.text;
    var newTextHandler = {
        init: origTextHandler.init,
        update: function (element, valueAccessor, allBindings, viewModel, bindingContext) {

            var bindings = allBindings();

            if (bindings.format) {
                // if there is a format, do the work to unwrap the value, then process it
                var value = ko.unwrap(valueAccessor());

                // if there is a format, check to see if it's a function, if so execute it, otherwise pass the value to the formatter
                if (_.isFunction(bindings.format)) {
                    value = bindings.format(value);
                } else {
                    value = newTextHandler.formatter(value, bindings.format);
                }

                origTextHandler.update(element, function () { return this; }.bind(value), allBindings, viewModel, bindingContext);
            } else {
                // if there isn't a format, don't mess with perfection, execute the original update
                origTextHandler.update(element, valueAccessor, allBindings, viewModel, bindingContext);
            }

        },
        formatter: function (toFormat,format)
        {
            if (_.isDate(toFormat)) {
                // if the value to format is a date, format it with moment
                return moment(toFormat).format(format);
            } else if (_.isUndefined(toFormat) || _.isNull(toFormat)) {
                // if the format is not defined, return nothing
                return undefined;
            } else {
                // if the value to format is defined, but we have no handle for it throw an exception
                throw new "Formatting not implemented for type " + typeof (toFormat);
            }
        }
    };
    ko.bindingHandlers.text = newTextHandler;