maps_objects.js

// Instantiate

const map = new Map([
  [1, "one"],
  [2, "two"],
]);

const obj = {
  1: "one",
  2: "two",
};

console.log({ map, obj });

// Set

map.set(3, "three");
obj[3] = "three";

// Get

console.log("map get", map.get(3));
console.log("obj get", obj[3]);

// Delete

map.delete(3);
delete obj[3];

// Keys

console.log("map keys", map.keys());
console.log("obj keys", Object.keys(obj));

// Has

console.log("map has key 1", map.has(2));
console.log("obj has key 1", 2 in obj);
console.log("obj has key 1", obj.hasOwnProperty(2));

// Values

console.log("map values", map.values());
console.log("obj values", Object.values(obj));

// Entries

console.log("map entries", map.entries());
console.log("obj entries", Object.entries(obj));

// Length

console.log("map size", map.size);
console.log("obj size", Object.keys(obj).length);

// Iteration for

for (const [key, value] of map) {
  console.log({ key, value });
}

for (const [key, value] of Object.entries(obj)) {
  console.log({ key, value });
}

// Iteration forEach

map.forEach((value, key) => console.log({ key, value }));
Object.entries(obj).forEach(([key, value]) => console.log({ key, value }));

// Swap Keys & Values

const swapMap = Array.from(map).reduce(
  (acc, [key, value]) => acc.set(value, key),
  new Map()
);

const swapObj = Object.entries(obj).reduce(
  (acc, [key, value]) => ({ ...acc, [value]: key }),
  {}
);

console.log({ swapMap, swapObj });