Looping and branching in JavaScript

Sourav.Kayal
Posted by in JavaScript category on for Beginner level | Points: 250 | Views : 7347 red flag

We will look into how to implement various loop and if else statement in JavaScript

Looping and branching in JavaScript

JavaScript is client side scripting language. Basically it is very light weight programming language which runs on client browser. As it is programming language it also supports few criteria to be a programming language like looping branching statement etc.

In this article we will see how to implement looping and branching in JavaScript. If you are familiar with looping and branching in other programming language then to understand this concept in JavaScript is a piece of cake for you.

Looping : As we know , loop is useful to do same operation again and again . Basically there are three popular loops are available in JavaScript. They are for, while and do-while.

Branching : Branching is very essential to execute program with respect to certain condition. Here we will see how to use if-else keyword to implement program flow.

Let’s start with Looping at first

For Loop:

In the code below,  for loop to go through all elements of array is implemented. We can use length property of JavaScript array to detect number of elements in array.

<html>
<head>
</head>
<body>
<script>
                var person=new Array();
                person[0]="sourav";
                person[1]="Sathis";
                person[2]="Nontey";
                for(var i = 0 ;i< person.length ;i++)
                {
                     document.write("Person " + i  + " : "+ person[i] + "<br>");
                }
</script>
</body>
</html>

While Loop:

In case of while loop there is only one condition within while() statement.

<html>
<head>
</head>
<body>
<script>
                var person=new Array();
                person[0]="sourav";
                person[1]="Sathis";
                person[2]="Nontey";
                var i =0;
                document.write("Using While loop" + "<br>");
                while(i < person.length)
                {
                    document.write("Person " + i  + " : "+ person[i] + "<br>");
                    i++;
                }
</script>
 
</body>
</html>

Do-While Loop

Do while is very similar with While loop but do- while is post checking loop. So, even if your condition is false loop will execute at least one time.

<html>
<head>
</head>
<body>
<script>
                var person=new Array();
                person[0]="sourav";
                person[1]="Sathis";
                person[2]="Nontey";
                var i =0;
                document.write("Using Do-While loop" + "<br>");
                do
                {
                   document.write("Person " + i  + " : "+ person[i] + "<br>");
                   i++;
                }while(i< person.length);
</script>
 
</body>
</html>


Branching:

Branching is common feature in all programming language. Using branch statement we can control program flow in code. Generally we can control program flow using if, else condition.  In case of more than one condition we may use ladder of if else or nested if else depending on situation.

Here we will see one simple example of if else in JavaScript and will try to understand implementation.

<html>
<head>
</head>
<body>
<script>
var x="";
var time=new Date().getHours();
if (time<20)
  {
                 x="Have Good day";
  }
else
  {
                x="Have Good evening";
  }
document.write(x);
               
</script>
</body>
</html>

In this example at first we are taking current hours using date function in JavaScript and then depending on hour we are showing message to user with the help of if –else statement.


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About the Author

Sourav.Kayal
Full Name: Sourav Kayal
Member Level: Silver
Member Status: Member,MVP
Member Since: 6/20/2013 2:09:01 AM
Country: India
Read my blog here http://ctrlcvprogrammer.blogspot.in/
http://www.dotnetfunda.com
I am .NET developer working for HelixDNA Technologies,Bangalore in healthcare domain. Like to learn new technology and programming language. Currently working in ASP.NET ,C# and other microsoft technologies.

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