Map and Set

const tags = new Set(["js", "web", "js", "react", "web"]);
console.log(tags);
console.log(tags.size);
console.log(tags.has("react"));

tags.add("css");
tags.delete("web");
console.log([...tags]);

const visits = ["home", "blog", "home", "about", "blog"];
const unique = [...new Set(visits)];
console.log(unique);

const a = new Set(["Asha", "Leo", "Mei"]);
const b = new Set(["Leo", "Raj"]);

const union = new Set([...a, ...b]);
const both = [...a].filter((x) => b.has(x));
const onlyA = [...a].filter((x) => !b.has(x));
console.log([...union], both, onlyA);

const prices = new Map();
prices.set("tea", 20);
prices.set("coffee", 35);
prices.set(42, "the answer");        // a number key

console.log(prices.get("coffee"));
console.log(prices.has("juice"));
console.log(prices.size);

for (const [item, price] of prices) {
  console.log(item, "→", price);
}

const words = "the cat and the hat and the bat".split(" ");
const counts = new Map();
for (const w of words) {
  counts.set(w, (counts.get(w) ?? 0) + 1);
}
console.log(counts);
console.log([...counts].sort((a, b) => b[1] - a[1])[0]);

const asha = { name: "Asha" };
const leo = { name: "Leo" };

const lastSeen = new Map();
lastSeen.set(asha, "today");
lastSeen.set(leo, "yesterday");
console.log(lastSeen.get(asha));