JS: Map.prototype.get

New in ES2015.

map_obj.get(key)

Return the value of the key key in map map_obj.

If key isn't found, return undefined.

const m = new Map([ [4, "n4"], [5, "n5"] ]);

// get the value of a key
console.log(m.get (5)); // "n5"

console.log(m.get (99)); // undefined

Reference

ECMAScript 2015 §Keyed Collection#sec-map.prototype.get