JavaScript Pocket Reference

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JavaScript Pocket Reference

while

The while statement is a basic loop. It repeatedly exe-

cutes a statement while an expression is

true:

while ( expression )

statement ;

with

The with statement adds an object to the scope chain, so

that a statement is interpreted in the context of the

object:

with ( object )

statement ;

The with statement has some complex and non-intuitive

side effects; its use is strongly discouraged.

Object-Oriented JavaScript

JavaScript objects are associative arrays that associate values

with named properties. JavaScript provides a simple inherit-

ance mechanism, and it is possible to define new classes of

objects for use in your own programs. To define a new class,

start by writing a constructor function. A constructor is like

any other function, except it is invoked with the

new opera-

tor and it uses the

this keyword to refer to and initialize the

newly created object. For example, here is a constructor to

create objects of a new class named

Point.

function Point(x,y) { // Constructor for Point

this.x = x; // Initialize X coordinate

this.y = y; // Initialize Y coordinate

}

Every JavaScript function used as a constructor has a property

named

prototype. This property refers to a special prototype

object for the class of objects created by the constructor. Any

properties you define on this prototype object are inherited by

all objects created with the constructor function. The proto-