JavaScript Logical Not (!) Operator


Logical NOT Operator

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

! symbol is used for logical NOT operator

!a

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

a!a
truefalse
falsetrue

Examples

1. check if 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