function displayInfo(args) {
    var output = "";
    
    if (typeof args.name == "string") {
        output += "Name:" + args.name + "\n";
    }
    
    if (typeof args.age == "number") {
        output += "Age:" + args.age + "\n";
    }
    
    alert(output);
}

displayInfo({
    name : "Nicholas",
    age : 29
});

displayInfo({
    name : "Greg";
});