{{deprecated_header()}}
Summary
Iterates a specified variable over all values of object's properties. For each distinct property, a specified statement is executed.
The for each...in statement is deprecated as the part of ECMA-357 (E4X) standard. E4X will be disabled by default and removed in the future, but for each...in will not be disabled and removed because of backward compatibility considerations. Consider using for...of instead. (Please refer to {{ bug("791343")}}.)
Version Information
Statement | |
Implemented in: | JavaScript 1.6 |
ECMAScript Version: | none |
Syntax
for each (variable in object) {
statement
}
Parameters
-
variable
-
Variable to iterate over property values, optionally declared with the
var
keyword. This variable is local to the function, not to the loop.
-
object
- Object for which the properties are iterated.
-
statement
-
A statement to execute for each property. To execute multiple statements within the loop, use a block statement (
{ ... }
) to group those statements.
Description
Some built-in properties are not iterated over. These include all built-in methods of objects, e.g. String
's indexOf
method. However, all user-defined properties are iterated over.
Examples
Example: Using for each...in
Warning: Never use a loop like this on arrays. Only use it on objects. Details.
The following snippet iterates over an object's properties, calculating their sum:
var sum = 0; var obj = {prop1: 5, prop2: 13, prop3: 8}; for each (var item in obj) { sum += item; } print(sum); // prints "26", which is 5+13+8
See also
- for...in - a similar statement that iterates over the property names.
- for...of - a similar statement that iterates over the property values but there is some behavior that is different from
for each...in
statements. - for
- Array comprehensions (these use
for each
) - Iterator - a function that takes a collection as an argument and allows traversal of its properties through subsequent methods