String.prototype.printf = function (obj) {
    var useArguments = false;
    var _arguments = arguments;
    var i = -1;
    if (typeof _arguments[0] == "string") {
        useArguments = true;
    }
    if (obj instanceof Array || useArguments) {
        return this.replace(/\%s/g, function (a, b) {
            i++;
            if (useArguments) {
                if (typeof _arguments[i] == 'string') {
                    return _arguments[i];
                } else {
                    throw new Error("Arguments element is an invalid type");
                }
            }
            return obj[i];
        });
    } else {
        return this.replace(/{([^{}]*)}/g, function (a, b) {
            var r = obj[b];
            return typeof r === 'string' || typeof r === 'number' ? r : a;
        });
    }
};