The Boolean object represents two values, either "true" or "false". If value parameter is omitted or is 0, -0, null, false, NaN, undefined, or the empty string (""), the object has an initial value of false.
Syntax
Use the following syntax to create a boolean object.
Boolean Properties
Here is a list of the properties of Boolean object:
Property
|
Description
|
constructor
|
Returns
a reference to
the Boolean function
that
|
created the object.
|
|
prototype
|
The prototype property allows you to add
properties
|
and methods to an object.
|
|
In the following sections, we will have a few
examples to illustrate the properties of Boolean object.
constructor ()
Javascript boolean constructor() method returns a reference to the Boolean function
that created the instance's prototype.
Syntax
Use the following syntax to create a Boolean constructor() method.
boolean.constructor()
Return Value
Returns the function that created this object's instance.
Example
Try the following example.
<html>
<head>
<title>JavaScript
constructor() Method</title>
</head>
<body>
<script
type="text/javascript">
var bool = new
Boolean( );
document.write("bool.constructor()
is : " + bool.constructor);
</script>
</body>
</html>
Output
bool.constructor()
is : function Boolean() { [native code] }
Prototype
The prototype property allows you to add
properties and methods to any object (Number, Boolean, String and Date, etc.).
Note: Prototype is a global
property which is available with almost all the objects.
Syntax
Use the following syntax to create a Boolean prototype.
object.prototype.name
= value
Example
Try the following example; it shows how to use
the prototype property to add a property to an object.
<html>
<head>
<title>User-defined
objects</title>
<script
type="text/javascript">
function
book(title, author){
this.title =
title;
this.author = author;
}
</script>
</head>
<body>
<script
type="text/javascript">
var
myBook = new book("Perl", "Mohtashim");
book.prototype.price = null; myBook.price = 100;
document.write("Book
title is : " + myBook.title + "<br>");
document.write("Book
author is : " + myBook.author + "<br>");
document.write("Book
price is : " + myBook.price + "<br>");
</script>
</body>
</html>
Output
Book title is :
Perl
Book author is :
Mohtashim
Book price is :
100
Boolean Methods
Here is a list of the methods of Boolean object and their description.
Method
|
Description
|
toSource() Returns a string containing the source of the
Boolean object; you can use this string to create an equivalent object.
toString() Returns a string of either "true" or
"false" depending upon the value of the object.
valueOf()
|
Returns the primitive
value of the Boolean object.
|
In the following sections, we will have a few
examples to demonstrate the usage of the Boolean methods.
toSource ()
Javascript boolean toSource() method returns a string representing the source code of
the object.
Note: This method is not compatible with all the
browsers.
Syntax
Its syntax is as follows:
boolean.toSource()
Return Value
Returns a string representing the source code of the object.
Example
Try the following example.
<html>
<head>
<title>JavaScript
toSource() Method</title>
</head>
<body>
<script
type="text/javascript">
function
book(title, publisher, price)
{
this.title =
title;
this.publisher =
publisher;
this.price =
price;
}
var newBook = new
book("Perl","Leo Inc",200);
document.write("newBook.toSource()
is : "+ newBook.toSource());
</script>
</body>
</html>
Output
({title:"Perl",
publisher:"Leo Inc", price:200})
toString ()
This method returns a string of either
"true" or "false" depending upon the value of the object.
Syntax
Its syntax is as follows:
boolean.toString()
Return Value
Returns a string representing the specified Boolean object.
Example
Try the following example.
<html>
<head>
<title>JavaScript
toString() Method</title>
</head>
<body>
<script
type="text/javascript">
var flag = new
Boolean(false);
document.write(
"flag.toString is : " + flag.toString() );
</script>
</body>
</html>
Output
flag.toString is :
false
valueOf ()
Javascript boolean valueOf() method returns the primitive value of the specified boolean object.
Syntax
Its syntax is as follows:
boolean.valueOf()
Return Value
Returns the primitive value of the specified boolean object.
Example
Try the following example.
<html>
<head>
<title>JavaScript
toString() Method</title>
</head>
<body>
<script
type="text/javascript">
var flag = new
Boolean(false);
document.write(
"flag.valueOf is : " + flag.valueOf() );
</script>
</body>
</html>
Output
flag.valueOf is :
false
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