Programming for beginners: JavaScript: Logical operators

JavaScript provides three logical operators, These are &&(AND), || (OR), and !(NOT)

Logical AND is also called Conditional AND

Logical OR is also called Conditional OR

Logical AND, OR are called Short circuit operators, will see why these are called short circuit soon.

Logical AND Operator

Operand1	Operand2	Evaluates To
true	true	true
true	false	false
false	true	false
false	false	false

Why Logical AND is called short circuit operator?

Since if the first statement in the expression evaluates to false, then Javascript won't evaluates the entire expression.

Logical OR Operator

Operand1	Operand2	Evaluates To
true	true	true
true	false	true
false	true	true
false	false	false

As shown in the above table, || operator returns true if any of the operand evaluates to true, otherwise returns false.

Why Logical OR is called short circuit operator?

Since if the first statement evaluates to true, then JavaScript won't evaluates the entire expression.

Logical (!)NOT operator

Operand	Evaluates To
false	true
true	false

If the operand is false, ! Operator evaluates it to true

If the operand is true, ! Operator evaluates it to false.

logical.html

<!DOCTYPE html>

<html>

<head>
    <title>Logical Operators</title>

    <style>
        p {
            font-size: 2em;
            color: seagreen;
        }
    </style>
</head>

<body>
    <p>
        <script type="text/javascript">
            var a = true;
            var b = true;
            var c = false;
            var d = false;

            document.write("a = " + a + "<br />");
            document.write("b = " + b + "<br />");
            document.write("c = " + c + "<br />");
            document.write("d = " + d + "<br />");

            document.write("a&&b = " + (a && b) + "<br />");
            document.write("a&&c = " + (a && c) + "<br />");
            document.write("c&&d = " + (c && d) + "<br /><br />");

            document.write("a||b = " + (a || b) + "<br />");
            document.write("a||c = " + (a || c) + "<br />");
            document.write("c||d = " + (c || d) + "<br />");
        </script>
    </p>
</body>

</html>

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Programming for beginners

Friday 24 August 2018

JavaScript: Logical operators

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