In JavaScript, booleans are the primitive data types that can either be true
or false
. For example,
const a = true;
const b = false;
Note: If you wrap true
or false
in a quote, then they are considered as a string.
For example,
const a = 'true';
console.log(typeof a); // string
The boolean values are mostly used for Comparison and Logical Operators. For example,
Equal to operator ==
returns true
if the operands are equal.
console.log(5 == 6); // false
Not equal to operator !=
returns true
if all the operands are not equal.
console.log(5 != 6); // true
Logical AND &&
returns true
if both the operand values are true
, else evaluates to false
.
console.log(true && false); // false
The boolean values are used in if...else
statements and for
loops as well.
Here's a list of values that gets converted to specific boolean values.
Data type | Boolean Value |
---|---|
undefined | false |
null | false |
NaN | false |
'' | false |
0 | false |
20 | true |
-20 | true |
'hello' | true |
JavaScript Boolean Methods
Here is a list of built-in boolean methods in JavaScript.
Method | Description |
---|---|
toString() |
returns a boolean value by converting boolean to a string |
valueOf() |
returns the primitive value of a boolean |
Example: Using toString()
let count = false;
// converting to string
let result = count.toString();
console.log(result);
console.log(typeof result);
Output
false string
Example: Using valueOf()
let count = true;
// converting to string
let result = count.valueOf();
console.log(result);
console.log(typeof result);
Output
true boolean
JavaScript Boolean() Function
The Boolean()
function is used to convert various data types to boolean values. For example,
const a = true;
console.log(Boolean(a)); // true
Everything with a value returns true
. For example,
let result;
result = 20;
console.log(Boolean(result)); // true
console.log(typeof Boolean(result)); // boolean
result = -20;
console.log(Boolean(result)); // true
result = 'hello';
console.log(Boolean(result)); // true
result = {a: 1};
console.log(Boolean(result)); // true
In JavaScript, undefined
, null
, 0, NaN
, ''
converts to false
. For example,
let result;
// empty string
result = Boolean('');
console.log(result); // false
result = Boolean(0);
console.log(result); // false
result = Boolean(undefined);
console.log(result); // false
result = Boolean(null);
console.log(result); // false
result = Boolean(NaN);
console.log(result); // false
Note: If you want to learn more about the boolean conversion, visit JavaScript Type Conversion.
Boolean Objects
You can also create a boolean value using the new
keyword. For example,
const a = true;
// creating a boolean object
const b = new Boolean(true);
console.log(a); // true
console.log(b); // true
console.log(typeof a); // "boolean"
console.log(typeof b); // "object"
Note: It is recommended to avoid using boolean objects. Using boolean objects slows down the program.