HTML and CSS Reference
In-Depth Information
The two additional values numbers can take on are
Infinity
and
NaN
. That's right,
NaN
is a number. (for more
information, see the section “Equality Checking”).
Strings
Strings are quite a bit simpler. As in most languages, you can treat a string like an array of characters. However, strings
are also objects, with numerous built-in properties and methods, such as
length
and
slice
:
> "example string"[0]
"e"
> "example string".length
14
> "example string".slice(7)
" string"
I should point out that what I'm doing in the previous example is particularly bad. The memory behavior of
where hard-coded strings are allocated isn't part of the language specification. Being allocated on the global heap is
actually one of the better scenarios. Depending on the browser, each individual use could be allocated separately on
the heap, further bloating your memory.
Booleans
Booleans, as in most languages, can take on the values
true
and
false
. Both are reserved keywords in JavaScript. The
main difference here between JavaScript and many other languages lies in which values can be coerced to either
true
or
false
(for further details, see the section “Truthiness,” later in this chapter).
Objects
Objects are the bread and butter of JavaScript, but they behave a bit differently from those in several other languages.
In many ways, objects are similar to dictionaries in modern interpreted languages:
x = {};
Curly braces indicate that you're defining an object. Nothing inside suggests that this is the empty object. You can
assign key-value pairs to an object like so:
player = { health: 10 };
Pretty simple, really. You can assign multiple key-value pairs to an object by separating them with a comma:
player = {
health: 10,
position: {
x: 325,
y: 210
}
};
Note in this example that you're assigning another object to the
position
property of
player
. This is entirely legal
in JavaScript and incredibly simple to do.
