@rbxts/jsnatives


union

Creates a new Set containing all elements from both sets.

Signature

function union<T>(set1: Set<T>, set2: Set<T>): Set<T>

Description

The union function combines two sets together, creating a new Set that contains all the elements from both input sets. If an element is present in both sets, it will appear only once in the resulting Set.

Parameters

Return value

Examples

Basic usage

// Create two sets with some numbers
const set1 = new Set([1, 2, 3, 4]);
const set2 = new Set([3, 4, 5, 6]);


// Combine both sets using union
const result = SetUtils.union(set1, set2);
console.log([...result]); // Outputs: [1, 2, 3, 4, 5, 6]

With string elements

// Sets with string elements
const fruits1 = new Set(["apple", "banana", "orange"]);
const fruits2 = new Set(["banana", "grape", "kiwi"]);


// Combine the fruit sets
const allFruits = SetUtils.union(fruits1, fruits2);
console.log([...allFruits]); // Outputs: ["apple", "banana", "orange", "grape", "kiwi"]

With mixed types

// Sets with mixed element types
const mixedSet1 = new Set([1, "hello", true]);
const mixedSet2 = new Set([2, "world", true]);


// Union of mixed type sets
const combinedMixed = SetUtils.union(mixedSet1, mixedSet2);
console.log([...combinedMixed]); // Outputs: [1, "hello", true, 2, "world"]

Empty sets

// Union with an empty set
const numbers = new Set([1, 2, 3]);
const empty = new Set();


// Union with an empty set returns a copy of the non-empty set
const result1 = SetUtils.union(numbers, empty);
console.log([...result1]); // Outputs: [1, 2, 3]


// Union of two empty sets returns an empty set
const result2 = SetUtils.union(empty, empty);
console.log([...result2]); // Outputs: []

Practical application

// Merging user permissions
function mergePermissions(basePermissions: Set<string>, rolePermissions: Set<string>): Set<string> {
  return SetUtils.union(basePermissions, rolePermissions);
}


// User has base permissions
const userPermissions = new Set(["read", "comment"]);


// User's role has additional permissions
const adminPermissions = new Set(["write", "delete", "moderate"]);


// Combine permissions
const effectivePermissions = mergePermissions(userPermissions, adminPermissions);
console.log([...effectivePermissions]);
// Outputs: ["read", "comment", "write", "delete", "moderate"]

Comparison with manual implementation

// Manual implementation of union operation
function manualUnion<T>(set1: Set<T>, set2: Set<T>): Set<T> {
  const result = new Set<T>(set1);
  for (const item of set2) {
    result.add(item);
  }
  return result;
}


// Using SetUtils.union
const set1 = new Set([1, 2, 3]);
const set2 = new Set([3, 4, 5]);


const manualResult = manualUnion(set1, set2);
const utilResult = SetUtils.union(set1, set2);


console.log([...manualResult]); // Outputs: [1, 2, 3, 4, 5]
console.log([...utilResult]);   // Outputs: [1, 2, 3, 4, 5]