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ASCII Character Set

American Standard Code for Information Interchange (ASCII) 7-bit character set widely used to represent letters and symbols found on a standard U.S. keyboard. The ASCII character set is the same as the first 128 characters (0–127) in the ANSI character set.

bitwise comparison

A bit-by-bit comparison of identically positioned bits in two numeric expressions.

Boolean expression

An expression that evaluates to either true or false. Non-Boolean expressions are converted to Boolean values, when necessary, according to the following rules:

• All objects are considered true.
• Strings are considered false if and only if they are empty.
• null and undefined are considered false.
• Numbers are considered false if and only if they are zero.

character code

A number that represents a particular character in a set, such as the ASCII character set.

comment

Text added to code by a programmer that explains how the code works. In JScript, a comment line generally starts with //. Use the /* and */ delimiters to create a multiline comment.

comparison operator

A character or symbol indicating a relationship between two or more values or expressions. These operators include less than (<), less than or equal to (<=), greater than (>), greater than or equal to (>=), not equal (!=), and equal (==).

compound statement

A sequence of statements enclosed in braces ({}). Can be used to perform multiple tasks any time a single statement is expected.

constructor

A JScript function that has two special features:

• It is invoked by the new operator.
• It is passed the address of a newly created object through the this keyword.

Use constructors to initialize new objects.

expression

A combination of keywords, operators, variables, and literals that yield a string, number, or object. An expression can perform a calculation, manipulate characters, call a function, or test data.

locale

The set of information that corresponds to a given language and country. A locale affects the language of predefined programming terms and locale-specific settings. There are two contexts where locale information is important:

• The code locale affects the language of terms such as keywords and defines locale-specific settings such as the decimal and list separators, date formats, and character sorting order.

• The system locale affects the way locale-aware functionality behaves, for example, when you display numbers or convert strings to dates. You set the system locale using the Control Panel utilities provided by the operating system.

null

A value indicating that a variable contains no valid data. null is the result of:

• An explicit assignment of null to a variable.
• Any operation between expressions that contain null.

numeric expression

Any expression that can be evaluated as a number. Elements of the expression can include any combination of keywords, variables, literals, and operators that result in a number. In certain circumstances, strings are also converted to numbers if possible.

property

A named attribute of an object. Properties define object characteristics such as size, color, and screen location, or the state of an object, such as enabled or disabled.

run-time error

An error that occurs when code is running. A run-time error results when a statement attempts an invalid operation.

scope

Defines the visibility of a variable, procedure, or object. Variables declared in functions are visible only within the function and lose their value between calls.

string comparison

A comparison of two sequences of characters. Unless specified in the function making the comparison, all string comparisons are binary. In English, binary comparisons are case-sensitive; text comparisons are not.

string expression

Any expression that evaluates to a sequence of continuguous characters. Elements of a string expression can include a function that returns a string, a string literal, a String object, or a string variable.

undefined

A special value given to variables after they are created and before a value has been assigned to them.

variable

A location used for storing and manipulating values by name. As JScript is loosely typed, a single variable can hold different types of data over the course of a script.