const map = new Map(); map.set("2019101","HongGilDong"); map.set("2019102","KimSaRang"); map.set("2019103","KandDongSu"); console.log("### Original data: forEach with Arrow") map.forEach((value, key) => console.log(key, value)); console.log("### Original data: for-of") for(let item of map ) { console.log(item[0],item[1]); } console.log("### Original data: for-of with key, map") for(let [key, value] of map ) { console.log(key,value); } console.log("### Original data: map.keys()") const keys = map.keys(); for(let key of keys) { console.log(map.get(key)); } console.log("### Map functions") console.log("get 201901: "+map.get("2019101")); map.delete("2019103") console.log("after delete 201903, has : ", map.has("2019103"));