​https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map​
Examples are in TypeScript.
const map: Map<string, string> = new Map();// Do not use []// This is badmap["key"] = "value";​// Do this insteadmap.get(key, value);
Taken from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map#Iterating_Map_with_for..of​
var myMap = new Map();myMap.set(0, 'zero');myMap.set(1, 'one');for (var [key, value] of myMap) {console.log(key + ' = ' + value);}// 0 = zero// 1 = one​for (var key of myMap.keys()) {console.log(key);}// 0// 1​for (var value of myMap.values()) {console.log(value);}// zero// one​for (var [key, value] of myMap.entries()) {console.log(key + ' = ' + value);}// 0 = zero// 1 = one