পৃষ্ঠাসমূহ

Search Your Article

CS

 

Welcome to GoogleDG – your one-stop destination for free learning resources, guides, and digital tools.

At GoogleDG, we believe that knowledge should be accessible to everyone. Our mission is to provide readers with valuable ebooks, tutorials, and tech-related content that makes learning easier, faster, and more enjoyable.

What We Offer:

  • 📘 Free & Helpful Ebooks – covering education, technology, self-development, and more.

  • 💻 Step-by-Step Tutorials – practical guides on digital tools, apps, and software.

  • 🌐 Tech Updates & Tips – simplified information to keep you informed in the fast-changing digital world.

  • 🎯 Learning Support – resources designed to support students, professionals, and lifelong learners.

    ✔ Latest world News 

     

Our Vision

To create a digital knowledge hub where anyone, from beginners to advanced learners, can find trustworthy resources and grow their skills.

Why Choose Us?

✔ Simple explanations of complex topics
✔ 100% free access to resources
✔ Regularly updated content
✔ A community that values knowledge sharing

We are continuously working to expand our content library and provide readers with the most useful and relevant digital learning materials.

📩 If you’d like to connect, share feedback, or suggest topics, feel free to reach us through the Contact page.

Pageviews

Friday, February 24, 2017

JavaScript - if...else Statement

While writing a program, there may be a situation when you need to adopt one out of a given set of paths. In such cases, you need to use conditional statements that allow your program to make correct decisions and perform right actions.

JavaScript supports conditional statements which are used to perform different actions based on different conditions. Here we will explain the if..else statement.

Flow Chart of if-else

The following flow chart shows how the if-else statement works.
Decision Making JavaScript supports the following forms of if..else statement −
  • if statement
  • if...else statement
  • if...else if... statement.

if statement

The if statement is the fundamental control statement that allows JavaScript to make decisions and execute statements conditionally.

Syntax

The syntax for a basic if statement is as follows −
if (expression){
   Statement(s) to be executed if expression is true
}
Here a JavaScript expression is evaluated. If the resulting value is true, the given statement(s) are executed. If the expression is false, then no statement would be not executed. Most of the times, you will use comparison operators while making decisions.

Example

Try the following example to understand how the if statement works.
<html>
   <body>
      
      <script type="text/javascript">
         <!--
            var age = 20;
         
            if( age > 18 ){
               document.write("<b>Qualifies for driving</b>");
            }
         //-->
      </script>
      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Qualifies for driving
Set the variable to different value and then try...

if...else statement:

The 'if...else' statement is the next form of control statement that allows JavaScript to execute statements in a more controlled way.

Syntax

if (expression){
   Statement(s) to be executed if expression is true
}

else{
   Statement(s) to be executed if expression is false
}
Here JavaScript expression is evaluated. If the resulting value is true, the given statement(s) in the ‘if’ block, are executed. If the expression is false, then the given statement(s) in the else block are executed.

Example

Try the following code to learn how to implement an if-else statement in JavaScript.
<html>
   <body>
   
      <script type="text/javascript">
         <!--
            var age = 15;
         
            if( age > 18 ){
               document.write("<b>Qualifies for driving</b>");
            }
            
            else{
               document.write("<b>Does not qualify for driving</b>");
            }
         //-->
      </script>
      
      <p>Set the variable to different value and then try...</p>
   </body>
</html>

Output

Does not qualify for driving
Set the variable to different value and then try...

if...else if... statement

The if...else if... statement is an advanced form of if…else that allows JavaScript to make a correct decision out of several conditions.

Syntax

The syntax of an if-else-if statement is as follows −
if (expression 1){
   Statement(s) to be executed if expression 1 is true
}

else if (expression 2){
   Statement(s) to be executed if expression 2 is true
}

else if (expression 3){
   Statement(s) to be executed if expression 3 is true
}

else{
   Statement(s) to be executed if no expression is true
}
There is nothing special about this code. It is just a series of if statements, where each if is a part of the else clause of the previous statement. Statement(s) are executed based on the true condition, if none of the conditions is true, then the else block is executed.

Example

Try the following code to learn how to implement an if-else-if statement in JavaScript.
<html>
   <body>
   
      <script type="text/javascript">
         <!--
            var book = "maths";
            if( book == "history" ){
               document.write("<b>History Book</b>");
            }
         
            else if( book == "maths" ){
               document.write("<b>Maths Book</b>");
            }
         
            else if( book == "economics" ){
               document.write("<b>Economics Book</b>");
            }
         
            else{
               document.write("<b>Unknown Book</b>");
            }
         //-->
      </script>
      
      <p>Set the variable to different value and then try...</p>
   </body>
<html>

Output

Maths Book
Set the variable to different value and then try...
Labels:

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)