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


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


Using size

var myMap = new Map();
myMap.set('a', 'alpha');
myMap.set('b', 'beta');
myMap.set('g', 'gamma');

myMap.size // 3


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

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support381219111258
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support383812191258 Yes

1. From Firefox 13 to Firefox 18, the size property was implemented as a Map.prototype.size() method, this has been changed to a property in later versions conform to the ECMAScript 2015 specification.

See also

Document Tags and Contributors

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