3D Game Programming

At first we’re not done with the game. Then, some time later, we are. If we

wrote code where it says, // do some work here, that code would think that the

game is still in progress. Being able to update variables will come in handy

shortly.

About that line that starts with two slashes...

Comments

Double slashes indicate comments. The computer knows it’s supposed to

ignore everything on the line that follows //. In other words, comments are for

people only:

// This returns today's date

vartoday =newDate();

// This is January 1, 2013

varjan1 =newDate(2013, 1, 1);

You Don’t Need to Type the Comments

The comments you see in this book are meant to give you helpful

hints. You don’t need to type them in, but you should. Comments

will help you to remember why you did things when you open your

code later to make a change.

Really, you should be adding your own comments as well.

7.3 Changing Things

We know that we can change things, but how can each kind of variable change

in JavaScript? Let’s take them one at a time.

Numbers

You can use standard math symbols to add and subtract numbers in Java-

Script. Try the following in the JavaScript console:

5 + 2;

10 - 9.5;

23 - 46;

84 + -42;

You should get back the following answers (the answer is shown in the com-

ments below the math problem).

5 + 2;

// 7

report erratum • discuss

Changing Things • 69

Prepared exclusively for Michael Powell