javascript objects as parameters not returning correct object

Question

I am working on a codecademy javascript course, and in this one i have to return the older age of two people. For some reason it is returning the younger age, cant figure it out for the life of me.

// Our person constructor
function Person (name, age) {
    this.name = name;
    this.age = age;
}
// We can make a function which takes persons as arguments
// This one computes the difference in ages between two people
var ageDifference = function(person1, person2){
    return person1.age - person2.age;
}
// Make a new function, olderAge, to return the age of
// the older of two people
function olderAge(){
    if(alice > billy){
        return alice.age;
    }
    else{
        return billy.age;
    }
}


// Let's bring back alice and billy to test our new function
var alice = new Person("Alice", 30);
var billy = new Person("Billy", 25);

console.log("The older person is " + olderAge(alice, billy));

How exactly you can define if an object is greater than another? — Teemu
– Teemu, Commented Jun 14, 2015 at 16:24

Cymen · Accepted Answer · 2015-06-14 17:46:02Z

2

Your function that compares ages is comparing the objects not the age parameter of the object. So this function:

function olderAge() {
  if (alice > billy) {
    return alice.age;
  } else {
    return billy.age;
  }
}

Should be:

function olderAge(a, b) {
  if (a.age > a.age) {
    return a.age;
  } else {
    return b.age;
  }
}

Putting it all together

I suggest changing your code to this -- we fix the olderAge:

// Our person constructor
function Person (name, age) {
    this.name = name;
    this.age = age;
}

// We can make a function which takes persons as arguments
// This one computes the difference in ages between two people
var ageDifference = function(person1, person2){
    return person1.age - person2.age;
}

// Make a new function, olderAge, to return the age of
// the older of two people
function olderAge(a, b) {
    if (a.age > b.age){
        return a.age;
    } else {
        return b.age;
  }
}


// Let's bring back alice and billy to test our new function
var alice = new Person("Alice", 30);
var billy = new Person("Billy", 25);

console.log("The older person is " + olderAge(alice, billy));

JSFiddle: http://jsfiddle.net/5ae24v92/2/

edited Jun 14, 2015 at 17:46

answered Jun 14, 2015 at 16:24

Cymen

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10 Comments

CASEY BAILEY Over a year ago

thank you, this is returning the correct age now. However, i am now getting this error.. Oops, try again. It looks like your olderAge function fails when the first Person is older! It should return the age of the older person

Felix Kling Over a year ago

@CASEYBAILEY: I guess the issue is that you are using global variables in olderAge, not the arguments passed to it.

Cymen Over a year ago

@FelixKling I glazed over that -- I updated with the fix.

CASEY BAILEY Over a year ago

thank you for your effor i am now getting "The older person is [object Object]" returned i think it is something to do with codecademy. some of there lessons are stupid specific

Cymen Over a year ago

@CASEYBAILEY On the JSFiddle, I added a toString method to the Person class. If you add that, the Person object will be converted to a string nicely.

|

Rayon · Accepted Answer · 2015-06-14 16:26:19Z

Try this:

<script>
    // Our person constructor
    function Person (name, age) {
        this.name = name;
        this.age = age;
    }
    // We can make a function which takes persons as arguments
    // This one computes the difference in ages between two people
    var ageDifference = function(person1, person2){
        return person1.age - person2.age;
    };
    // Make a new function, olderAge, to return the age of
    // the older of two people
    function olderAge(){
        if(alice.age > billy.age){
            return alice.age;
        }else{
            return billy.age;
        }
    }
    // Let's bring back alice and billy to test our new function
    var alice = new Person("Alice", 30);
    var billy = new Person("Billy", 25);
    console.log("The older person is " + olderAge(alice, billy));
</script>

You missed the ".age" in comparison..

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