JavaScript NOT

JavaScript NOT Operator is used to invert the value of a boolean condition.

NOT Operator Symbol

The symbol used for NOT Operator is !.

Syntax

The syntax to use NOT Operator with an operand a is

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Copy
!a

a can be a Boolean variable, or boolean expression, or a complex condition.

NOT Truth Table

The following truth table provides the output of NOT operator for different values of operands.

a!a
truefalse
falsetrue

NOT Operator negates the given value.

Examples

In the following example, we take a boolean variable with different values: true and false, and find their logical NOT output.

index.html

<!DOCTYPE html>
<html lang="en">
<body>
    <pre id="output"></pre>
    <script>
        var a = true;
        var result = !a;
        document.getElementById('output').innerHTML += '\n!' + a + '   is  ' + result;

        a = false;
        result = !a;
        document.getElementById('output').innerHTML += '\n!' + a + '  is  ' + result;
    </script>
</body>
</html>

In the following example, we will use NOT operator for a boolean condition in If Statement.

index.html

<!DOCTYPE html>
<html lang="en">
<body>
    <pre id="output"></pre>
    <script>
        var a = 4;
        if (!(a % 2 == 0)) {
            document.getElementById('output').innerHTML += a + ' is not even.';
        } else {
            document.getElementById('output').innerHTML += a + ' is even.';
        }
    </script>
</body>
</html>

Conclusion

In this JavaScript Tutorial, we learned about Logical NOT Operator, its syntax, and usage with examples.