Formats a date given the supplied format string.
@param {Date} date The date to format
@param {String} format The format string
@return {String} The formatted date or an empty string if date parameter is not a JavaScript Date object
function(date, format) {
        var formatFunctions = utilDate.formatFunctions;

        if (!Ext.isDate(date)) {
            return '';
        }

        if (formatFunctions[format] == null) {
            utilDate.createFormat(format);
        }

        return formatFunctions[format].call(date) + '';
    }