↑
Main Page

Types

Netscape’s proposal introduces several new types:

Never

— Has no values

Void

— Replaces the Undefined type from ECMAScript Edition 3

Integer

— All integer values

char

— All single 16-bit Unicode characters

Type

— The supertype of all types

Unlike ECMAScript Edition 3, all types are considered objects and not primitive values.

New

machine types

represent primitive number values:

sbyte

— Signed byte integer, values between –128 and 127

byte

— Byte integer, values between 0 and 255

short

— Short integer, values between –32768 and 32767

ushort

— Unsigned short integer, values between 0 and 65535

int

— Integer, values between –2147483648 and 2147483647

uint

— Unsigned integer, values between 0 and 4294967295

long

— Long integer, values between –9223372036854775808 and 9223372036854775807

ulong

– Unsigned long integer, values between 0 and 18446744073709551615

float

— Floating-point number, all single precision IEEE floating-point numbers

The machine types can be used in place of regular types whenever a number must be represented. For

example:

var b : byte = 10;

var longnum : long = L100;

Classes

A class in ECMAScript Edition 4 (per the Netscape proposal) takes a form like this:

class MyClass {

private var color : String = “red”;

public function MyClass(color : String) {

this.color = color;

}

public function sayColor() : Void {

alert(this.color);

}

601

The Evolution of JavaScript

23_579088 ch20.qxd 3/28/05 11:44 AM Page 601