- JavaScript Tutorial
- JavaScript Advantages and Disadvantages
- Adding JavaScript to html
- External JavaScript JS File – Advantages, Disadvantages, Syntax, Attributes
- JavaScript Syntax
- JavaScript Statements
- JavaScript Output
- JavaScript Comments
- Javascript Data Types
- JavaScript Variables
- JavaScript Scope of Variables
- JavaScript Operators
- Javascript ternary operator
- Javascript typeof Operator
- Javascript Arithmetic Operators
- Javascript Assignment
- JavaScript Functions
- JavaScript Anonymous Functions
- JavaScript Callback Functions
- JavaScript Objects
- JavaScript Events
- JavaScript Strings
- JavaScript String Methods
- JavaScript Numbers
- JavaScript Number Methods
- JavaScript Math Object
- JavaScript Date
- JavaScript Date Formats
- JavaScript Date Methods
- JavaScript Arrays
- JavaScript Array Methods
- JavaScript Boolean
- JavaScript Comparisons
- JavaScript Conditions
- JavaScript Switch statement
- JavaScript For loop
- JavaScript while loop
- JavaScript Break and Continue
- JavaScript Type Conversion
- JavaScript Regular Expressions
- JavaScript Errors
- JavaScript Debugging
- JavaScript Conventions
- JavaScript Best Practices
- JavaScript Common Mistakes
- JavaScript Reserved Words
- JavaScript Performance
- JSON Data, format, mime type and parsing
- JavaScript Form Validation
- Forms API
- JavaScript Objects Definition
- JavaScript Object Properties
- JavaScript Object Methods
- JavaScript Object Prototypes
- JavaScript Window Object
- JavaScript Window Screen
- JavaScript Cookies
- JavaScript Location Object
- JavaScript History
- JavaScript Window Navigator
JavaScript Boolean
The Boolean datatype represents either TRUE or FALSE value.
The Boolean datatype is mostly used with conditional statements to do different actions and change control flow based on condition which returns Boolean TRUE or FALSE
In programming, often we require a variable which holds any one value from two values like..
True / False Active / Inactive On / Off Yes / No
JavaScript Boolean data type is used to store either true of false value.
Boolean() function
Boolean() function is used to find out if an expression or a variable is true or false.
<!DOCTYPE html>
<html>
<body>
Boolean returns True / False based on expression or variable.
<p id="text"></p>
<script>
var a = 5;
var b = 0;
document.getElementById('text').innerHTML = Boolean(a > b);
</script>
</body>
</html>Download the code Run the code
An expression always return true or false, it is not necessary to use Boolean() function
<!DOCTYPE html>
<html>
<body>
It is not necessary to use Boolean() function an expression always returns True / False based on expression or variable.
<p id="text"></p>
<script>
var a = 5;
var b = 0;
document.getElementById('text').innerHTML = a > b;
</script>
</body>
</html>Download the code Run the code
Boolean data type is mostly used with comparison operators and conditional statements which is described in detail in upcoming chapters.
Everything with a real value is True.
All variables having a values other than 0 and empty string is evaluates to true.
<!DOCTYPE html>
<html>
<body>
Real values evaluates to true.
<p id="text"></p>
<script>
document.getElementById('text').innerHTML = '500 is ' + Boolean(500) +
'<br> 2.5 is ' + Boolean(2.5) +
'<br> -50 is ' + Boolean(-50) +
'<br> India is ' + Boolean("India") +
'<br> False is ' + Boolean("India") +
'<br> 1+2+3 is ' + Boolean(1+2+3) +
'<br> 1.5+2.5 is ' + Boolean(1.5+2.5) +
'<br> 1 > 0 is ' + Boolean(1 > 0) +
'<br> -5 < 5 is ' + Boolean(-5 < 5);
</script>
</body>
</html>Download the code Run the code
Everything without a real value is False.
All variables or expressions having a 0 value or empty string evaluates to false.
<!DOCTYPE html>
<html>
<body>
0 and empty string evalutes to false.
<p id="text"></p>
<script>
document.getElementById('text').innerHTML = '0 is ' + Boolean(0) +
'<br> -0 is ' + Boolean(-0) +
'<br> empty string is ' + Boolean("");
</script>
</body>
</html>Download the code Run the code
Undefined evaluates to false.
Undefined is always evaluates to false.
<!DOCTYPE html>
<html>
<body>
Undefined evaluates to false.
<p id="text"></p>
<script>
var num;
document.getElementById('text').innerHTML = 'undefined is ' + Boolean(undefined) +
'<br />num is ' + Boolean(num);
</script>
</body>
</html>Download the code Run the code
Null evaluates to false.
null is always evaluates to false.
<!DOCTYPE html>
<html>
<body>
Null evaluates to false.
<p id="text"></p>
<script>
var start=null;
document.getElementById('text').innerHTML = 'start is null and evaluates to ' + Boolean(start);
</script>
</body>
</html>Download the code Run the code
NaN evaluates to false.
NaN is always evaluates to false.
<!DOCTYPE html>
<html>
<body>
Null evaluates to false.
<p id="text"></p>
<script>
var sum= 5 * "five";
alert(sum);
document.getElementById('text').innerHTML = 'sum is NaN and evaluates to ' + Boolean(sum);
</script>
</body>
</html>Download the code Run the code
Note: Boolean values do not have any properties or methods