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interesting aspect of ECMAScript

Pascal Notation — the first letter is uppercase and each appended word begins with an upper-

case letter. For example:

var MyTestValue = 0, MySecondTestValue = “hi”;

Hungarian Type Notation — prepends a lowercase letter (or sequence of lowercase letters) to

the beginning of a Pascal Notation variable name to indicate the type of the variable. For exam-

ple,

means integer and

means string in the following line:

var iMyTestValue = 0, sMySecondTestValue = “hi”;

The following table list prefixes for defining ECMAScript variables with Hungarian Type Notation.

These prefixes are used throughout the book to make sample code easier to read:

Type

Prefix

Example

Array

aValues

Boolean

bFound

Float (Number)

fValue

Function

fnMethod

Integer (Number)

iValue

Object

oType

Regular Expression

rePattern

String

sValue

Variant (can be any type)

vValue

Another interesting aspect of ECMAScript (and a major difference from most programming languages)

is that variables don’t have to be declared before being used. For example:

var sTest = “hello “;

sTest2 = sTest + “world”;

alert(sTest2); //outputs “hello world”

In the previous code,

sTest

is declared with a string value of

“hello”

. The next line uses a variable

named

sTest2

to create a concatenation of

sTest

and the string

“world”

. The variable

sTest2

hasn’t

been defined using the

var

operator; it has just been inserted as if it has already been declared.

When the ECMAScript interpreter sees an identifier that hasn’t been declared, it creates a global variable

with the given name of the identifier and initializes it with the value specified. This is a handy feature of

the language, but it can also be dangerous if you don’t keep track of variables closely. Best practice is

always to declare all variables as you would with other programming languages (for more information

on why you should always declare variables, see Chapter 19, “Deployment Issues”).

Chapter 2

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