Node.js

const map = new Map();
map.set("foo", "bar");

let found = map.has("foo");
console.log(found);

let item = map.get("foo");
console.log(item);

map.delete("foo");

found = map.has("foo");
console.log(found);

item = map.get("foo");
console.log(item);

const map2 = {};
map2["foo"] = "bar";
item = map2["foo"];
delete map2["foo"];

const map3 = new Map();
map3.set("foo", 100);
map3.set("bar", 200);
map3.set("baz", 300);

for (let [key, value] of map3) {
  console.log(key, value);
}

Output

true
bar
false
undefined
foo 100
bar 200
baz 300

Go

package main

import "fmt"

func main() {
	map1 := make(map[string]string)

	map1["foo"] = "bar"

	item, found := map1["foo"]
	fmt.Println(found)
	fmt.Println(item)

	delete(map1, "foo")

	item, found = map1["foo"]
	fmt.Println(found)
	fmt.Println(item)

	map2 := make(map[string]int)
	map2["foo"] = 100
	map2["bar"] = 200
	map2["baz"] = 300

	for key, value := range map2 {
		fmt.Println(key, value)
	}
}

Output

true
bar
false

foo 100
bar 200
baz 300