Javascript Reference Card printable pdf download

Addison-Wesley’ s

JavaScript Reference Card

Kathleen M. Goelz and Carol J. Schwartz, Rutgers University

Javascript: A scripting language designed to be integrated

VARIABLES

into HTML code to produce enhanced, dynamic, interac-

Definition: A placeholder for storing data. In JavaScript, a

tive web pages.

declaration statement consists of the reserved word var and

the name (identifier) of one or more variables.

DATA TYPES

Format:

Definition: The classification of values based on the specific

var variable_name

categories in which they are stored.

[var command is used to declare (create) variables]

Primitive Types: String, Boolean, Integer, Floating Point,

Examples:

Null, Void

var myHouseColor

Composite Types: Object, Array, Function. Composite data

var myAddress

types are in separate sections of the code.

var vacation_house, condominium,

primaryResidence

NUMERIC

Rules for Naming Variables:

Integer: Positive or negative numbers with no fractional

1. Variables cannot be reserved words.

parts or decimal places.

2. Variables must begin with a letter or underscore and

Floating Point: Positive or negative numbers that contain a

cannot begin with symbols, numbers, or arithmetic

decimal point or exponential notations.

notations.

String: A sequence of readable characters or text, surround-

3. Spaces cannot be included in a variable name.

ed by single or double quotes.

Hints:

Boolean: The logical values True/False, etc. used to com-

1. Although variables in JavaScript can be used without

pare data or make decisions.

being declared, it is good programming practice to

Null: The variable does not have a value; nothing to report.

declare (initialize), all variables.

Null is not the same as zero, which is a numeric value.

2. Variable names are case sensitive; for example X does

Casting: Moving the contents of a variable of one type to a

not equal x.

variable of a different type. You don’t move the contents to

a different variable; it stays in the same variable but the

data type is changed or “re-cast”.

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ISBN 0-321-32075-1

Javascript Reference Card

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