JavaScript Code

Logical NOT Operator

Logical NOT operator takes an operand, and returns true if given operand if false, or false if given operand if true.

Syntax

! symbol is used for logical NOT operator.

!a

Truth Table of NOT Gate

The following truth table provides the output of NOT operator for possible operand values.

a	!a
true	false
false	true

Examples

1. Check if value in num is not positive.

let num = -11;
if (!(num > 0)) {
    console.log('num is not positive');
} else {
    console.log('num is positive');
}

in the above example, operand a is (num > 0) which is to check if num is positive, but the condition that we need to check is if num is not positive. so, we use not operator to negate the condition (num > 0), thus our required condition of checking if num is not positive happens.