Looping
 
for - - in
 

This loop is used with arrays and objects , to access their elements and properties respectively.

In for..in looping the variable starts from zero and increases itself with one until it reach to the length of array.

 
Syntax:
 

for( variablename in objectname)

{

lines to be executed

}

 
Example:
 

<html>

<head>

</head>

<body>

<script type="text/javascript">

var color;

var shop=new Array()

shop[0]="Red"

shop[1]="Blue"

shop[2]="Green"

shop[3]="Yellow"

shop[4]="Magenta"

for(color in shop)

{

document.write("<br> "+shop[color]);

}

</script >

</body>

</html>

 
Understanding program:
Color is a undefined variable and shop is an array, when color is kept as a subscript of array shop then the color variable becomes of number type and from 0 to 4 gets incremented by for - in loop. It is increased up to 4 only because shop array have 5 elements and an array start from 0 position.
 
Output is:
Red
Blue
Green
Yellow
Magenta
Click here to view result of this program on browser
Click here to see the animation of Looping.(With Voice)