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The forEach()
method executes a provided function once per each value in the Set
object, in insertion order.
Syntax
mySet.forEach(callback[, thisArg])
Return value
Parameters
callback
- Function to execute for each element.
thisArg
- Value to use as
this
when executingcallback
.
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
The 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 an 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 2017 Draft (ECMA-262) The definition of 'Set.prototype.forEach' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 38 | 25.0 (25.0) | 11 | 25 | 7.1 |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | No support | 38 | 25.0 (25.0) | No support | No support | 8 |