JavaScript Booleans

In JavaScript, a Boolean is a primitive data type that can only have one of two values:

true or false

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

• true and false are boolean data types
• true and false are the only possible boolean values
• true and false must be written in lowercase
• true and false must be written without quotes

Very often, in programming, you will need a data type that can represent one of two values, like:

• yes or no
• on or off
• true or false

Boolean values are fundamental for logical operations and control flow in JavaScript programming.

All JavaScript comparison operators (like ==, !=, <, >) return true or false from the comparison.

Given that x = 5 , the table below explains comparison:

Booleans are extensively used in if statements to determine the code blocks to execute based on the logic.

JavaScript if else

Booleans are extensively used in loops to determine conditions for looping.

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

In JavaScript, both an empty array [ ] and an empty object { } are truthy because they are objects.

All objects in JavaScript evaluate to true in a boolean context, regardless of their content.

Normally JavaScript booleans are primitive values created from literals:

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

The new keyword complicates the code and slows down execution speed.