JavaScript Booleans

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JavaScript Booleans


A JavaScript Boolean represents one of two values: true or
false.

Boolean Values
Very often, in programming, you will need a data type that can only have one
of two values, like

YES / NO
ON / OFF
TRUE / FALSE

For this, JavaScript has a Boolean data type. It can only
take the values true or false.

The Boolean() Function
You can use the Boolean() function to find out if an expression (or a variable) is
true:

Example

Boolean(10 > 9)

Try it Yourself »

Or even easier:

Example

(10 > 9)
10 > 9

Try it Yourself »


Comparisons and Conditions
The chapter JS Comparisons gives a full overview of comparison operators.
The chapter JS Conditions gives a full overview of conditional statements.
Here are some examples:


Operator
Description
Example


==
equal to
if (day == "Monday")


>
greater than
if (salary > 9000)


<
less than
if (age < 18)



The Boolean value of an expression is the basis for all JavaScript comparisons and conditions.








Everything With a "Value" is True

Examples

100
3.14
-15
"Hello"
"false"
7 + 1 + 3.14
Try it Yourself »


Everything Without a "Value" is False

The Boolean value of 0 (zero) is false:

let x = 0;
Boolean(x);

Try it Yourself »


The Boolean value of -0 (minus zero) is false:

let x = -0;
Boolean(x);

Try it Yourself »


The Boolean value of "" (empty string) is false:

let x = "";
Boolean(x);

Try it Yourself »


The Boolean value of undefined is false:

let x;
Boolean(x);

Try it Yourself »


The Boolean value of null is false:

let x = null;
Boolean(x);

Try it Yourself »


The Boolean value of false is (you guessed it) false:

let x = false;
Boolean(x);

Try it Yourself »


The Boolean value of NaN is false:

let x = 10 / "Hallo";
Boolean(x);

Try it Yourself »


JavaScript Booleans as Objects
Normally JavaScript booleans are primitive values created from literals:


let x = false;


But booleans can also be defined as objects with the keyword new:


let y = new Boolean(false);



Example

let x = false;
let y = new Boolean(false);
//
typeof x returns boolean
//
typeof y returns object

Try
it yourself »


Do not create Boolean objects.
The new keyword complicates the code and slows down execution speed.
Boolean objects can produce unexpected results:


When using the == operator, x and y are equal:

let x = false;
let y = new Boolean(false);

Try it Yourself »


When using the === operator, x and y are not equal:

let x = false;
let y = new Boolean(false);

Try it Yourself »


Note the difference between (x==y) and (x===y).


(x == y) true or false?

let x = new Boolean(false);
let y = new Boolean(false);

Try it Yourself »


(x === y) true or false?

let x = new Boolean(false);
let y = new Boolean(false);

Try it Yourself »


Comparing two JavaScript objects always return false.


Complete Boolean Reference
For a complete reference, go to our Complete
JavaScript Boolean Reference.
The reference contains descriptions and examples of all Boolean properties and methods.












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Reference: https://www.w3schools.com/js/js_booleans.asp