var isNumeric = function(n) {
    return !isNaN(parseFloat(n)) && isFinite(n)
};

var multiplyNumeric = function(obj) {
    for (var key in obj) {
    	(isNumeric(obj[key])) ? obj[key] *= 2 : obj[key];
    }
};

var menu = {
    width: 400,
    height: 600,
    title: "My menu"
};

multiplyNumeric(menu);

alert(menu.title);