Map.prototype.has()

The has() method returns a boolean indicating whether an element with the specified key exists or not.

Syntax

has(key)

true if an element with the specified key exists in the Map object; otherwise false.

let myMap = new Map()
myMap.set('bar', "foo")

myMap.has('bar')   // returns true
myMap.has('baz')   // returns false

Specification
ECMAScript Language Specification # sec-map.prototype.has

	desktop						mobile						server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on iOS	Samsung Internet	Deno	Node.js
`has`	ChromeFull support38	EdgeFull support12	FirefoxFull support13	Internet ExplorerFull support11	OperaFull support25	SafariFull support8	WebView AndroidFull support38	Chrome AndroidFull support38	Firefox for AndroidFull support14	Opera AndroidFull support25	Safari on iOSFull support8	Samsung InternetFull support3.0	DenoFull support1.0	Node.jsFull support0.12.0