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The size accessor property returns the number of elements in a Set object.


The value of size is an integer representing how many entries the Set object has. A set accessor function for size is undefined; you cannot change this property.


Using size

var mySet = new Set();
mySet.add('some text')

mySet.size; // 3


Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Set.prototype.size' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'Set.prototype.size' in that specification.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support 38 (Yes) 19 (19) [1] 11 25 7.1
Feature Android Chrome for Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support 38 (Yes) 19.0 (19) No support No support 8

[1] From Gecko 13 (Firefox 13 / Thunderbird 13 / SeaMonkey 2.10) to Gecko 18 (Firefox 18 / Thunderbird 18 / SeaMonkey 2.15 / Firefox OS 1.0.1 / Firefox OS 1.1) the size property was implemented as a Set.prototype.size() method, this has been changed to a property in later versions conform to the ECMAScript 6 specification (bug 807001).

See also

Document Tags and Contributors

 Contributors to this page: jameshkramer, nmve, kdex, fscholz, Zambonifofex, realityking
 Last updated by: jameshkramer,