org.htmlunit.corejs.javascript

Class Undefined

java.lang.Object

org.htmlunit.corejs.javascript.Undefined

All Implemented Interfaces:

Serializable

public class Undefined
extends Object
implements Serializable

This class implements the Undefined value in JavaScript.

We represent "undefined" internally using two static objects -- "Undefined.instance" and SCRIPTABLE_UNDEFINED. Java code that needs to make something undefined should generally use the first, and use the second if a Scriptable object is absolutely required.

Java code that needs to test whether something is undefined must use the "isUndefined" method because of the multiple internal representations.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static Object	instance This is the standard value for "undefined" in Rhino.
static Scriptable	SCRIPTABLE_UNDEFINED An alternate representation of undefined, to be used only when we need to pass it to a method that takes as Scriptable as a parameter.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object obj)
int	hashCode()
static boolean	isUndefined(Object obj) Safely test whether "obj" is undefined.
Object	readResolve()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

instance

public static final Object instance

This is the standard value for "undefined" in Rhino. Java code that needs to represent "undefined" should use this object (rather than a new instance of this class).

SCRIPTABLE_UNDEFINED

public static final Scriptable SCRIPTABLE_UNDEFINED

An alternate representation of undefined, to be used only when we need to pass it to a method that takes as Scriptable as a parameter. This is used when we need to pass undefined as the "this" parmeter of a Callable instance, because we cannot change that interface without breaking backward compatibility.

Method Detail

readResolve

public Object readResolve()

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

isUndefined

public static boolean isUndefined(Object obj)

Safely test whether "obj" is undefined. Java code must use this function rather than testing the value directly since we have two representations of undefined in Rhino.