Modifying Objects

This is just a screen grab of our interactive coding talk-through, prepared to make captioning and translation easier. It is better to watch our talk-throughs here:
https://www.khanacademy.org/cs/programming/

And we're back! This time, our program has the Winston object,

but we're only displaying the age of Winston. That's because I wanna show

you how we could change Winston's age. Because you know eventually,

Winston has to get older. Let's remember what it would be like if we were

just using simple variables. We have var winston age equals 19, and then if we

wanted to change it, we would say winston age equals 20.

and that would change the value stored in that variable. It's really really similar

for object properties. We can just say winston dot age equals 20, and then we've changed

the value stored in the age property of the Winston object.

Cool.

So let's see if that worked. We'll take our text command, put it below,

change the y, tada! Winston got older. So easy.

Um, okay, so now let's try, we were just adding one here

let's do that more programatically. Let's say winston dot age equals winston dot age plus one.

So what we're saying here is take the previous value of his age

add one to it, and then store it in the age property.

And that should just end up adding one to whatever the previous value was. Let's see.

Display it, tada! He's 21.

Getting getting so old. All right. Now, remember we have a shortcut for adding one

to variables, and the same shortcut works with object properties so we can say winston dot age plus plus

And let's see if that worked. Yup! And that really just did exactly the same thing as this line,

it's just a shortcut, so that we don't have to type as much.

Now if we look at all this, this really looks like the situation for a loop.

We keep on using the same code over and over, and the only thing we're changing is we're adding one

to his age, and we're changing the y position so it's on a different line.

So, if we used a loop, it could be really easy to show him getting older and older and older

and not have to use that much code. Let's say, we'll make a loop to show Winston getting to 40 years old.

He doesn't wanna get any older than that because then he'd be wrinkly

and we'd have to call him "Wrinkleston." [laugh]

All right.

So we'll do a while loop and we'll say while winston dot age is less than or equal to 40

and then inside here, we're gonna display his age

and we're going to add one to his age each time.

Okay, that worked, but everything is piled on top of each other, so we need to change the y position

each time. And we'll just do winston dot age times 20, um, minus 200, minus 300

Okay! and we'll just minus 350. All right. That looks good. Let's delete the old stuff here.

Tada! Now we can see Winston getting older and older, but not so old that he'll be a Wrinkleston.

Okay. So, now we can see how to change age, we can also add additional information in the

Winston object as he gets older. Like, maybe when he turns 30, he'll meet another programmer

named Winnefer, and he'll marry her.

And no, he's not just gonna marry her because she has such a great name.

So what we can do is we can add a property by just saying winston dot, and then the new

property key which will be wife, equals Winnefer.

Great, but, we only want him to have this wife when he's at, you know, at a good marrying age

so we'll say equals 30 and we'll go and move, move that inside here.

Great. So now he has a wife, so, you know, they're happy, and then they have some kids

a couple years later, so maybe when they're, uh, 32, we'll add some kids to the object

to keep track of that. And they have twins, of course, cause they're very productive

And Winston's twins will be named, uh, of course Winston Junior and Winstonia.

Beautiful. That's a, that's a great family. Great set of names.

And so you can see we can add new properties that are strings and arrays

and anything we could've had in the original object.

And so once this loop finishes, winston dot age will be 40, and winston will

have a wife, who's Winnefer, and a twins, which is a set of er, which an array of two names.

Huh. That's an awesome loop. But, hey, if you don't like how this story ends for Winston,

you could always spin off this program and tell your own story of his future

now that you know all about how to change object properties.