Package org.mozilla.javascript
Class Undefined
- java.lang.Object
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- org.mozilla.javascript.Undefined
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- All Implemented Interfaces:
java.io.Serializable
public class Undefined extends java.lang.Object implements java.io.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
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Field Summary
Fields Modifier and Type Field Description static java.lang.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.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
equals(java.lang.Object obj)
int
hashCode()
static boolean
isUndefined(java.lang.Object obj)
Safely test whether "obj" is undefined.java.lang.Object
readResolve()
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Field Detail
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instance
public static final java.lang.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).
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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.
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Method Detail
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readResolve
public java.lang.Object readResolve()
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equals
public boolean equals(java.lang.Object obj)
- Overrides:
equals
in classjava.lang.Object
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hashCode
public int hashCode()
- Overrides:
hashCode
in classjava.lang.Object
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isUndefined
public static boolean isUndefined(java.lang.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.
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