Google Maps API 3

CHAPTER 3 ■ CREATING YOUR FIRST MAP
Booleans
Booleans can have only two values, true or false. This might not seem much, but it’s actually the logic
on which computers are constructed—you know, ones and zeros. You can actually use 1 instead of true
and 0 instead of false since they mean the same thing. Actually, any numbers except 0 will return true,
so all you’ll need to remember is that 0 is false.
var male = true;
var female = 0; // false
■ Tip You might have noticed that I always include a semicolon at the end of each line of code. This is actually
optional in JavaScript, but I strongly suggest that you always use semicolons since omitting them makes
the JavaScript interpreter guess where they should be. This leads to slower performance and potentially hardto-find
bugs.
Functions
Functions are one of the core features of a programming language. They are perfect for reusing code. A
simple function that will throw an alert with the classic phrase “Hello world” looks like this:
function message() {
alert('Hello world!');
}
To execute it, you call it by its name, including its parentheses:
message();
This will result in the alert shown in Figure 3-4 being thrown.
Figure 3-4. Hello world!
All it does right now is to throw the alert “Hello world” each time you call it, but if you want it to be a
bit more useful, such as throwing an alert with a phrase of your choice, then you need to provide it with
arguments. Arguments are used to pass values to the function.
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