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The forEach()
method executes a provided function once for each value in the Set
object, in insertion order.
The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.
Syntax
mySet.forEach(
function callback(value1, value2, Set) { //your iterator }[, thisArg])
Parameters
callback
- Function to execute for each element. See Description for details.
value1, value2
- The value contained in the the current position in the Set. The same value is passed for both arguments.
Set
- The Set object that's being traversed.
thisArg
- Value to use as
this
when executingcallback
.
Return value
Description
The forEach()
method executes the provided callback
once for each value which actually exists in the Set
object. It is not invoked for values which have been deleted. However, it is executed for values which are present but have the value undefined
.
callback
is invoked with three arguments:
- the element value
- the element key
- the
Set
object being traversed
There are no keys in Set
objects. However, the first two arguments are both values contained in the Set
, so that the callback function is consistent with the forEach()
methods for Map
and Array
.
If a thisArg
parameter is provided to forEach()
, it will be passed to callback
when invoked, for use as its this
value. Otherwise, the value undefined
will be passed for use as its this
value. The this
value ultimately observable by callback
is determined according to the usual rules for determining the this
seen by a function.
Each value is visited once, except in the case when it was deleted and re-added before forEach()
has finished. callback
is not invoked for values deleted before being visited. New values added before forEach()
has finished will be visited.
forEach()
executes the callback
function once for each element in the Set
object; it does not return a value.
Examples
Logging the contents of a Set
object
The following code logs a line for each element in a Set
object:
function logSetElements(value1, value2, set) { console.log('s[' + value1 + '] = ' + value2); } new Set(['foo', 'bar', undefined]).forEach(logSetElements); // logs: // "s[foo] = foo" // "s[bar] = bar" // "s[undefined] = undefined"
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Set.prototype.forEach' in that specification. |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) The definition of 'Set.prototype.forEach' in that specification. |
Draft |
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Basic support | Chrome Full support 38 | Edge Full support 12 | Firefox Full support 25 | IE Full support 11 | Opera Full support 25 | Safari Full support 8 | WebView Android Full support 38 | Chrome Android Full support 38 | Edge Mobile Full support 12 | Firefox Android Full support 25 | Opera Android Full support 25 | Safari iOS Full support 8 | Samsung Internet Android Full support Yes | nodejs Full support 0.12 |
Legend
- Full support
- Full support