Looping In javaScript

Loops are used to execute a set of statements repeatedly until a particular condition is satisfied

The basic purpose of loop is to execute set of statements until condition becomes false and same code repeated again and again.

Advantage

It is used to reduce length of Code

It takes less memory space.

Types of Loops

There are three types of loop available in javaScript

·         while loop

·         for loop

·         do-while
  While loop

In while loop  First check the condition if condition is true then the control goes inside the loop body and  print the output , It will repeated again and again until condition becomes false. If condition becomes false control goes outside the body and loop is terminated

Syntax:

assignment;

while(condition){    

Statements;   

………….

Increment/decrement (++,--)

} 

Example:

  <script>  

  var i=1;  

  while (i<=5)  {  

  document.write(i + "<br/>");  

  i++;  }  

  </script> 

Output:

1

2

3

4

5

Note: If while loop condition never false then loop becomes infinite loop

do-while
First print output then checks the condition. Since condition is checked later, the body statements will execute at least once
Syntax:

assignment;

do

{    

Statements;   

………….

Increment/decrement(++,--)

      }

    while(condition); 

Example:

  <script>  

  var i=1;  

  do{  

  document.write(i + "<br/>");  

   i++;

    }  

  while (i<=5);  

  </script> 

Output:

1

2

3

4

5

For loop

for loop is used to iterate a program several times and execute the code repeatedly.

We can initialize variable, check condition and increment/decrement value.

Syntax:

      for(initialization; condition; increment/decrement)

    {    

      //Statement

      }    

Example:

  <script>  

  for (i=1; i<=5; i++)  {  

  document.write(i + "<br/>")  }  

  </script>  

Output:

1

2

3

4

5

Break

break is used to break loop or switch statement.

Syntax:

statement;      

break;  

Example:

<script>

     for(int i=1;i<=5;i++){     

            if(i==4){   

               

                break;     

            }     

   document.write(i + "<br/>")  

        }   

</script>    

Output:

1

2

3

Continue

continue statement is used to continue loop.

Syntax:

Statement;

continue;   

Example:

<script>

     for(int i=1;i<=5;i++){     

            if(i==3){   

               

                continue;     

            }     

  document.write(i + "<br/>")  

        }   

</script>    

Output:

1

2

4

5