JavaScript Booleans

Boolean is a primitive data type in JavaScript. Boolean can have only two values, true or false. It is useful in controlling program flow using conditional statements like if..else, switch, while, do..while.


Boolean Function

Boolean() function can be used to find if an expression is true

JS JavaScript - Boolean Function

<!DOCTYPE html>
 
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
    <body>
    <h1>Booleans</h1>
    <p>Play around with Booleans</p>
     
    <button onclick="testBooleans()">Click me to test</button>
    <button onclick="testDonald()">Test Donald</button>
     
    <script>
        function testBooleans() {
            var result = "No result";
             
            if (4 > 2) {
                result = "Comparison is true";
            }
            else {
                result = "Comparison is false";
            }
             
            document.getElementById("resultElement").innerHTML = result;
            }
             
        function testDonald() {
            var result = "My name is Dick";
             
            var name = "Donald";
             
            if(name == "Donald") {
                result = "My name is Donald";
        }
         
        document.getElementById("resultElement").innerHTML = result;
        }
    </script>
     
    <p id="resultElement"></p>
    </body>
</html>

Learn more about JavaScript Conditions

Boolean Comparison

JS JavaScript - Boolean Comparison

Operator Description Example
== Equal To if(x == 20)
> Greater Than if(x > 20)
< Less Than if(x < 20)
>= Greater Than Or Equal To x >= 20
<= Less Than Or Equal To x <= 20
AND True When Both Operands are true if(age>20 && age <30)
OR True When One Of The Operands are true if(age==20 || age ==30)
NOT Toggles a statement from true to false or
from false to true
if(!(age==20))
=== Equal Value And Equal Type var x = 20;
if(x === 20)    // true
if(x === "20") // false
!= Not Equal if(age != 20)
!== Not Equal Value OR Not Equal Type var x = 20;
if(x !== 20)     // false
if(x === "20") // true

Learn more about JavaScript Comparisons

Conditional

The conditional (ternary) operator is the only JavaScript operator that takes three operands. This operator is frequently used as a shortcut for the if statement

 

JS JavaScript - Conditional

<!DOCTYPE html>
 
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
    <body>
    <h1>Booleans</h1>
    <p>Play around with Booleans</p>
     
    <button onclick="testBooleans()">Click me to test</button>
     
    <script>
    function testBooleans() {
        var age = 66;
        var testDriveCar = (age < 16) ? 'Too young to drive':'You are old enough to drive';
         
        document.getElementById("resultElement").innerHTML = testDriveCar;
    }
    </script>
     
    <p id="resultElement"></p>
    </body>
</html>

Comparing Different Types

Comparing data of different types may give unexpected results.

JavaScript will convert the string to a number when comparing a string with a number. An empty string converts to 0. A non-numeric string converts to NaN (Not A Number) and will always be false.


Case Boolean Description
20 > 30 false Comparing two numbers
20 > "30" false Converting "30" to number 30
20 > "Donald"
20 < "Donald"
20 == "Donald"
false String converts to NaN
"20" > "30" false Converts both strings to numbers
before comparing them
"20" < "30" true Converts both strings to numbers
before comparing them
"20" == "30" false Converts both strings to numbers
before comparing them
"30" == "30" true Converts both strings to numbers
before comparing them


Convert To Correct Type

Convert variables to the proper type before comparison to ensure a correct result

JS JavaScript - Convert To Correct Type

// Validate input to check if it is a number
if (isNaN(input)) {
    output = "Please add a number";
} else {
    output = (input < 20) ? "You are not old enough" : "You are old enough to enter";
}

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Check this out

JS JavaScript: Numbers Methods

Number methods can help you when working with number datatypes. The number methods are improved in ES6 (ECMAScript 6).

Keep reading to understand how the number methods and properties may help you.

JS JavaScript: Bitwise Operators

Bitwise operators will handle their operands as a sequence of 32 bits (zeroes and ones), and not like decimal, hexadecimal, or octal numbers. For example, the decimal number nine has a binary representation of 1001. Bitwise operators perform their operation....

JS JavaScript: Events

Events are actions or occurrences that happen to HTML elements.

JavaScript can act when an HTML Event occurs.

Events can represent everything from basic user interactions to automated notifications of things happening in the rendering model.

JS JavaScript: Strict Mode

The strict context prevents some actions and throws more exceptions. Strict mode changes previously accepted "bad syntax" into errors. Strict mode will for example prevent using undeclared variables. The "use strict" directive was new in ECMAScript version 5.


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JavaScript is one of the 3 core language technologies of the World Wide Web that all web developers must learn:

1.      HTML to define the content of web pages.

2.      CSS to specify the layout of web pages.

3.      JavaScript to program the behavior of web pages.

JavaScript is a scripting or programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at, displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. − you can bet that JavaScript is probably involved.


The benefits of using JavaScript are:

1.      You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.

2.      Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something.

3.      Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.

4.      Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.


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Update Conference Prague is the biggest developer conference in the Czech Republic. The conference is offering sessions delivered by the top experts from all around the world. Their goal is to inspire the attendees and enrich their knowledge.

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W3Schools

W3Schools.com is a great education Web Site for learning web technologies. On W3Schools you may find well organized basic to advanced tutorials and references.

Scott Hanselman

Learn about Web Technologies and new trends from Scott Hanselman. Scott Hanselman is an author of developer books and he is an engaged speaker that usually talks about the Microsoft stack. You may meet Scott on conferences around the world.

Developer Week

DeveloperWeek is one of the world’s largest developer conferences. Developer Week focus on new dev technologies, the conference have talks and workshops for newbies and experienced audience. You can attend on a Developer Week conference different places in Nothern America.


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