Curriculum

JavaScript Basic

JSHome

0/216

JS Versions

0/36

JS Objects

0/15

JS Funtions

0/22

JS Classes

0/3

JS Async

0/10

JS HTML DOM

0/25

JS Browser BOM

0/17

JS Web APIs

0/7

JS AJAX

0/11

JS JSON

0/16

JS vs jQuery

0/4

JS Graphics

0/7

Text lesson

JS Booleans

Boolean Values

In programming, you frequently require a data type that can have one of two values, such as

YES / NO
ON / OFF
TRUE / FALSE

For this purpose, JavaScript provides the Boolean data type, which can only be true or false.

The Boolean() Function

You can use the Boolean() function to determine whether an expression (or variable) evaluates to true.

Example

Boolean(10 > 9)

Or even more simply:

Example

(10 > 9)
10 > 9

Comparisons and Conditions

The chapter on JS Comparisons provides a comprehensive overview of comparison operators.

The chapter on JS If Else offers an in-depth look at conditional statements.

Here are a few examples:

Operator	Description	Example
==	equal to	if (day == “Monday”)
>	greater than	if (salary > 9000)
<	less than	if (age < 18)

Everything With a “Value” is True

Examples

100

3.14

–15

“Hello”

“false”

7 + 1 + 3.14

Everything Without a “Value” is False

The Boolean value of 0 (zero) is considered false.

let x = 0;
Boolean(x);

The Boolean value of -0 (minus zero) is also considered false.

let x = –0;
Boolean(x);

The Boolean value of an empty string (“”) is evaluated as false.

let x = “”;
Boolean(x);

The Boolean value of undefined is regarded as false.

let x;
Boolean(x);

The Boolean value of null is considered false.

let x = null;
Boolean(x);

The Boolean value of false is, as expected, false.

let x = false;
Boolean(x);

The Boolean value of NaN is false:

let x = 10 / “Hallo”;
Boolean(x);