TypeScript Set

// Explicitly typed empty Set
const stringSet = new Set<string>();

// Type inferred as Set<number>
const numberSet = new Set([1, 2, 3, 3]); // Internal state: {1, 2, 3}

// Union types
const mixedSet = new Set<string | number>();

const registry = new Set<number>();

// Mutation
registry.add(100).add(200); 

// Inspection
const exists = registry.has(100); // true
const count = registry.size;      // 2

// Deletion
const removed = registry.delete(200); // true
registry.clear();                     // size is now 0

interface Config {
    retries: number;
}

const configSet = new Set<Config>();
const defaultConfig = { retries: 3 };

configSet.add(defaultConfig);
configSet.add(defaultConfig); // Ignored, same reference
configSet.add({ retries: 3 }); // Added, different reference

console.log(configSet.size); // 2

const tokens = new Set<string>(['alpha', 'beta', 'gamma']);

// Iterable protocol
for (const token of tokens) {
    console.log(token);
}

// Callback-based iteration
// Note: 'value' and 'key' are identical in Sets to maintain compatibility with Map's forEach signature.
tokens.forEach((value: string, key: string, set: Set<string>) => {
    console.log(value === key); // true
});

const evens = new Set<number>([2, 4, 6, 8]);
const primes = new Set<number>([2, 3, 5, 7]);

// Elements in either set
const union = evens.union(primes); // Set {2, 4, 6, 8, 3, 5, 7}

// Elements in both sets
const intersection = evens.intersection(primes); // Set {2}

// Elements in 'evens' but not in 'primes'
const difference = evens.difference(primes); // Set {4, 6, 8}

// Elements in either set, but not both
const symmetricDifference = evens.symmetricDifference(primes); // Set {4, 6, 8, 3, 5, 7}

// Boolean subset/superset checks
const isSubset = new Set([2, 4]).isSubsetOf(evens); // true
const isSuperset = evens.isSupersetOf(new Set([2])); // true