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Boolean : Object

The Boolean object is an object wrapper for a boolean value.

Browser/User Agent Support

IEMozillaNetscapeOperaSafari
3.0+1.0+3.0+7.0+1.0+

Constructors

ConstructorIEMozillaNetscapeOperaSafari
Boolean Constructor
Creates a new instance of a Boolean object.
3.0+1.0+3.0+7.0+1.0+
 

Properties

PropertyIEMozillaNetscapeOperaSafari
constructor
Specifies the function that creates the Boolean prototype.
4.0+1.0+3.0+7.0+1.0+
 
prototype
Represents the Boolean prototype object.
4.0+1.0+3.0+7.0+1.0+
 

Methods

MethodIEMozillaNetscapeOperaSafari
toSource
Returns a string representing the source code of a Boolean object.
4.0+1.0+4.0+nono
 
toString
Returns a string representing the specified Boolean object.
4.0+1.0+3.0+7.0+1.0+
 
valueOf
Returns the primitive value of a Boolean object.
4.0+1.0+3.0+7.0+1.0+
 

Creating Boolean objects with an initial value of false

bNoParam = new Boolean();
bZero = new Boolean(0);
bNull = new Boolean(null);
bEmptyString = new Boolean("");
bfalse = new Boolean(false);

Creating Boolean objects with an initial value of true

btrue = new Boolean(true);
btrueString = new Boolean("true");
bfalseString = new Boolean("false");
bSuLin = new Boolean("Su Lin");

Remarks

Do not confuse the primitive Boolean values true and false with the true and false values of the Boolean object.

Any object whose value is not undefined or null, including a Boolean object whose value is false, evaluates to true when passed to a conditional statement. For example, the condition in the following if statement evaluates to true:

x = new Boolean(false);
if (x) //the condition is true

This behavior does not apply to Boolean primitives. For example, the condition in the following if statement evaluates to false:

x = false;
if (x) //the condition is false

Do not use a Boolean object to convert a non-boolean value to a boolean value. Instead, use Boolean as a function to perform this task:

x = Boolean(expression);     //preferred
x = new Boolean(expression); //don't use

If you specify any object, including a Boolean object whose value is false, as the initial value of a Boolean object, the new Boolean object has a value of true.

myFalse = new Boolean(false);   // initial value of false
g = new Boolean(myFalse);       //initial value of true
myString = new String("Hello"); // string object
s = new Boolean(myString);      //initial value of true

Do not use a Boolean object in place of a Boolean primitive.

References

Object

Availability

JavaScript 1.1 | JScript 2.0 | ECMAScript v1

Constructor Detail

Boolean Boolean(Boolean value)

Creates a new instance of a Boolean object.

BooleanvalueThe initial value of the Boolean object. The value is converted to a boolean value, if necessary. If value is omitted or is 0, -0, null, false, NaN, undefined, or the empty string (""), the object has an initial value of false. All other values, including any object or the string "false", create an object with an initial value of true.

Property Detail

Object constructor -  only

Specifies the function that creates the Boolean prototype.

See Also

Object.constructor

Availability

JavaScript 1.1 | JScript 2.0 | ECMAScript v1

Visibility

Object prototype -  only

Represents the Boolean prototype object.

See Also

Function.prototype

Availability

JavaScript 1.1 | JScript 2.0 | ECMAScript v1

Visibility

Method Detail

toSource() :  String

Returns a string representing the source code of a Boolean object.

Remarks

The toSource method returns the following values:

  • For the built-in Boolean object, toSource returns the following string indicating that the source code is not available: 
function Boolean() {
   [native code]
}
  • For instances of Boolean, toSource returns a string representing the source code.

This method is usually called internally by JavaScript and not explicitly in code.

See Also

Object.toSource

Availability

JavaScript 1.3

toString() : String

Returns a string representing the specified Boolean object.

Remarks

The Boolean object overrides the toString method of the Object object; it does not inherit Object.toString. For Boolean objects, the toString method returns a string representation of the object.

JavaScript calls the toString method automatically when a Boolean is to be represented as a text value or when a Boolean is referred to in a string concatenation.

For Boolean objects and values, the built-in toString method returns the string "true" or "false" depending on the value of the boolean object. In the following code, flag.toString returns "true".

var flag = new Boolean(true)
var myVar=flag.toString()
Availability

JavaScript 1.1 | JScript 2.0 | ECMAScript v1

valueOf() : Boolean

Returns the primitive value of a Boolean object.

Using valueOf

x = new Boolean();
myVar=x.valueOf()      //assigns false to myVar
Remarks

The valueOf method of Boolean returns the primitive value of a Boolean object or literal Boolean as a Boolean data type.

This method is usually called internally by JavaScript and not explicitly in code.

Throws
Throws TypeError if the object is not a Boolean.
See Also

Object.valueOf

Availability

JavaScript 1.1 | JScript 2.0 | ECMAScript v1