JavaScript NOT (!) Operator

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

!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
true	false
false	true

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.