for each...in
The for each...in
statement is deprecated as the part of ECMA-357 (E4X) standard. E4X support has been removed, 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.)
The for each...in
statement iterates a specified variable over all values of object's properties. For each distinct property, a specified statement is executed.
Syntax
for each (variable in object) { statement }
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
Using for each...in
Warning: Never use a loop like this on arrays. Only use it on objects. See for...in
for more 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; } console.log(sum); // logs "26", which is 5+13+8
Specifications
Not part of a current ECMA-262 specification. Implemented in JavaScript 1.6 and deprecated.
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | No support | 1.5 (1.8) | No support | No support | No support |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | No support | No support | 1.0 (1.0) | No support | No support | No support |
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 can only be used for iteratable types, so not for generic objectsfor
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/javascript/reference/statements/for_each...in