Question

I’m getting the next error in function getOlder():
TypeError: Cannot read property ‘age’ of undefined

What’s the problem and how to fix it?

function person(name, age) {
    this.name=name;
    this.age=age
}

// Returns the older person in a group of persons.
var getOlder = function(people) {
    if (people.length === 0) {
        return new person();
    }

    var older = people[0]; // The first one is the older for now.

    var value;
    for (var _ in people) {
        value = people[_];
        if (value.age > older.age) {
            older = value;
        }
    }
    return older;
};

// Declare some persons.
var paul = new person("Paul", 23);
var jim = new person("Jim", 24);
var sam = new person("Sam", 84);
var rob = new person("Rob", 54);
var karl = new person("Karl", 19);

var older = getOlder(paul, jim);
if (older.name !== "Jim") {
    console.log("Fail");
}

Answer 1

var getOlder = function() {
    var people = arguments;
    if (people.length === 0) {
        return new person();
    }

    var older = people[0]; // The first one is the older for now.

    var value;
    for (var _ in people) {
        value = people[_];
        if (value.age > older.age) {
            older = value;
        }
    }
    return older;
   };

By Accepting no arguments in the function definition and relying on the variable arguments feature of JS you can get away with calling getOlder(paul, jim).

arguments is a property of every function which is basically an array of variable arguments provided to it while calling .