JavaScript Booleans

Introduction to Booleans

In JavaScript, booleans are a data type that can only have two values: true or false. They are typically used to represent the truth value of an expression or condition in a program. For example, you might use a boolean to represent whether a user is logged in to your website or not.

let loggedIn = true;

In the above example, loggedIn is a boolean variable that is set to true.

Comparison Operators and Booleans

Booleans are often used in conjunction with comparison operators to evaluate expressions. Comparison operators are used to compare two values and return a boolean value. Here are some of the comparison operators in JavaScript:

• == equal to
• != not equal to
• > greater than
• < less than
• >= greater than or equal to
• <= less than or equal to

let x = 5;
let y = 10;

console.log(x < y); // outputs true
console.log(x == y); // outputs false

In the above example, x is less than y, so console.log(x < y) returns true. x is not equal to y, so console.log(x == y) returns false.

Logical Operators and Booleans

Logical operators are used to combine or invert boolean expressions. There are three logical operators in JavaScript:

• && logical and
• || logical or
• ! logical not

let a = true;
let b = false;

console.log(a && b); // outputs false
console.log(a || b); // outputs true
console.log(!a); // outputs false

In the above example, console.log(a && b) returns false because a is true and b is false. console.log(a || b) returns true because at least one of a or b is true. console.log(!a) returns false because the logical not operator inverts the value of a.