for...in Statement (Windows Scripting - JScript)

 

Executes one or more statements for each property of an object, or each element of an array.

Syntax

for (variable in [object | array])
   statements 

Arguments

• variable
  Required. A variable that can be any property name of object or any element index of an array.

• object, array
  Optional. An object or array over which to iterate.

• statements
  Optional. One or more statements to be executed for each property of object or each element of array. Can be a compound statement.

Remarks

Before each iteration of a loop, variable is assigned the next property name of object or the next element index of array. You can then use it in any of the statements inside the loop to reference the property of object or the element of array.

When iterating over an object, there is no way to determine or control the order in which the members of the object are assigned to variable. Iterating through an array will be performed in element order, that is, 0, 1, 2, ...

The following example illustrates the use of the for ... in statement with an object used as an associative array.

// Initialize object.
a = {"a" : "Athens" , "b" : "Belgrade", "c" : "Cairo"}

// Iterate over the properties.
var s = ""
for (var key in a)
    {
    s += key + ": " + a[key];
    s += "<br />";
    }
document.write (s);

// Output:
// a: Athens
// b: Belgrade
// c: Cairo

This example illustrates the use of the for ... in statement to iterate though a JScript Array object that has expando properties.

// Initialize the array.
var arr = new Array("zero","one","two");

// Add a few expando properties to the array.
arr["orange"] = "fruit";
arr["carrot"] = "vegetable";

// Iterate over the properties and elements.
var s = "";
for (var key in arr)
{
    s += key + ": " + arr[key];
    s += "<br />";
}

document.write (s);

// Output:
//   0: zero
//   1: one
//   2: two
//   orange: fruit
//   carrot: vegetable

Note

Use the Enumerator object to iterate members of a collection.

Requirements

Version 5

Change History

Date	History	Reason
March 2009	Modified first example and added second example.	Information enhancement.

See Also

for Statement (Windows Scripting - JScript)
while Statement (Windows Scripting - JScript)