@rbxts/jsnatives


difference

Creates a new Set containing elements that exist in the first set but not in the second set.

Signature

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

Description

The difference function creates a new Set containing only the elements that are present in the first set but not in the second set. It is sometimes referred to as the "relative complement" of the second set in the first set.

Parameters

Return value

Examples

Basic usage

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


// Find elements in set1 that are not in set2
const result = SetUtils.difference(set1, set2);
console.log([...result]); // Outputs: [1, 2]

With string elements

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


// Find fruits in first set that are not in second set
const uniqueFruits = SetUtils.difference(fruits1, fruits2);
console.log([...uniqueFruits]); // Outputs: ["apple", "orange"]

Order matters

// Difference is not commutative - order matters
const set1 = new Set([1, 2, 3]);
const set2 = new Set([2, 3, 4]);


// set1 - set2
const result1 = SetUtils.difference(set1, set2);
console.log([...result1]); // Outputs: [1]


// set2 - set1
const result2 = SetUtils.difference(set2, set1);
console.log([...result2]); // Outputs: [4]

Empty and identical sets

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


// set - empty = set
const result1 = SetUtils.difference(numbers, empty);
console.log([...result1]); // Outputs: [1, 2, 3]


// empty - set = empty
const result2 = SetUtils.difference(empty, numbers);
console.log([...result2]); // Outputs: []


// Difference with identical sets
const set = new Set([1, 2, 3]);
const sameset = new Set([1, 2, 3]);
const result3 = SetUtils.difference(set, sameset);
console.log([...result3]); // Outputs: []

Practical application

// Remove banned users from active users list
function removeInactiveMemberships(allUsers: Set<string>, inactiveUsers: Set<string>): Set<string> {
  return SetUtils.difference(allUsers, inactiveUsers);
}


// All users
const allUsers = new Set([
  "user1", "user2", "user3", "user4", "user5"
]);


// Inactive users to be removed
const inactiveUsers = new Set([
  "user2", "user5"
]);


// Get active users only
const activeUsers = removeInactiveMemberships(allUsers, inactiveUsers);
console.log([...activeUsers]);
// Outputs: ["user1", "user3", "user4"]

Filtering items

// Filter out items that match certain criteria
function filterSelectedItems<T>(allItems: Set<T>, excludeItems: Set<T>): Set<T> {
  return SetUtils.difference(allItems, excludeItems);
}


// Shopping cart items
const cartItems = new Set(["shirt", "pants", "hat", "shoes", "socks"]);


// Items on backorder (unavailable)
const backorderedItems = new Set(["hat", "shoes"]);


// Get only available items
const availableItems = filterSelectedItems(cartItems, backorderedItems);
console.log([...availableItems]);
// Outputs: ["shirt", "pants", "socks"]

Comparison with manual implementation

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


// Using SetUtils.difference
const set1 = new Set([1, 2, 3, 4, 5]);
const set2 = new Set([4, 5, 6, 7]);


const manualResult = manualDifference(set1, set2);
const utilResult = SetUtils.difference(set1, set2);


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