18. The Boolean Type

The Boolean type represents logical entities and can only have two values: true or false. They are fundamental for making decisions in code (control flow).

Defining Booleans

javascript const isLoggedIn = true; let isAdmin = false;

Booleans from Comparison

Booleans are typically generated by comparison operators (covered in detail soon).

javascript let a = 10; let b = 5;

let isGreater = (a > b); // Is 10 greater than 5? Yes. console.log(isGreater); // Output: true

let isEqual = (a === b); // Is 10 strictly equal to 5? No. console.log(isEqual); // Output: false

Boolean Context (Truthiness)

In decision structures (like if statements), JS automatically converts values to a boolean state. This is called truthiness.

Falsy Values (Convert to false):

• false
• 0 (the number zero)
• '' (an empty string)
• null
• undefined
• NaN

Truthy Values (Convert to true):

• Everything else (e.g., 1, 'hello', [], {})