Set opterations on 2 arrays: intersection, difference, union

array-set-operations.js

// Intersection
let intersection = arrA.filter(x => arrB.includes(x));

// Difference
let difference = arrA.filter(x => !arrB.includes(x));

// Symmetrical Difference 1st syntax
let symmetricalDifference = arrA
  .filter(x => !arrB.includes(x))
  .concat(arrB.filter(x => !arrA.includes(x)));

// Symmetrical Difference 2nd syntax
let left = arrA.filter(x => !arrB.includes(x));
let right = arrB.filter(x => !arrA.includes(x));
let symmetricalDifference = [...left, ...right];

// Union (unique values)
let union = [...new Set([...arrA, ...arrB)];
                        
// Equals (primitive values only)
let isEqual = arrA.every(value => arrB.includes(value)) && arrB.every(value => arrA.includes(value));

// Unique filter 1st syntax
const uniqueFilter = (value, index, array) => array.indexOf(value) === index;
let unique = arrA.filter(uniqueFilter);

// Unique filter 2nd syntax
let unique = [...new Set(arrA)];

// toggle (add/remove) an item in an array
export function toggleInArray<T>(arr: T[], item: T) {
  return arr.includes(item) ? arr.filter(i => i !== item) : [...arr, item];
}