The for...in statement is used to loop (iterate) through the elements of an array or through the properties of an object.
The code in the body of the for ... in loop is executed once for each element/property.
for (variable in object)
code to be executed
The variable argument can be a named variable, an array element, or a property of an object.
Using for...in to loop through an array:
var mycars = new Array()
mycars = "Saab"
mycars = "Volvo"
mycars = "BMW"
for (x in mycars)
document.write(mycars[x] + "