for...in Statement

Microsoft® JScript™
for...in / for...of Statements
Language Reference
Version 1

Description

Executes a statement for each element of an object or array.

Syntax

for (variable in [object | array])
statement
for (variable of array)
statement
The for statement syntax has these parts:

Part Description

variable In the for...in statement, a variable that can hold any of the elements of object or the name of an index in the array. The variable is a string, which is set to match each of the keys in the object.

In the for..of statement, variable is a number, which indexes the array. Note that it may not iterate the array in order.

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

statement The statement to be executed for each member of object. Can be a compound statement.

Remarks

Before each iteration of a loop, variable is assigned the next element of object. You can then use it in any of the statements inside the loop exactly as if you were using the element of object.
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.
See the continue Statement.

Comments:

Part	Description
variable	In the for...in statement, a variable that can hold any of the elements of object or the name of an index in the array. The variable is a string, which is set to match each of the keys in the object. In the for..of statement, variable is a number, which indexes the array. Note that it may not iterate the array in order.
object, array	An object or array over which to iterate.
statement	The statement to be executed for each member of object. Can be a compound statement.