Find duplicate emails (or any data type) in an array and the intersection, difference, symmetrical difference, and union of two arrays.

array-sets.js

const dataA = []

const dataB = []

const arrA = dataA.map(e => e.toLowerCase().replace(/\s/g, ''));
const arrB = dataB.map(e => e.toLowerCase().replace(/\s/g, ''));

console.log(arrA.length, arrB.length)

// Find duplicates in array A
let duplicatesA = []
const tempArray = [...arrA].sort()
for (let i = 0; i < tempArray.length; i++) {
  if (tempArray[i + 1] === tempArray[i]) {
    duplicatesA.push(tempArray[i])
  }
}
console.log(duplicatesA, duplicatesA.length);

// Find duplicates in array B
let duplicatesB = []
const tempArray = [...arrB].sort()
for (let i = 0; i < tempArray.length; i++) {
  if (tempArray[i + 1] === tempArray[i]) {
    duplicatesB.push(tempArray[i])
  }
}
console.log(duplicatesB, duplicatesB.length);

// Array intersection
let intersection = arrA.filter(x => arrB.includes(x));
console.log(intersection, intersection.length);

// Array difference (in A and not in B)
let difference1 = arrA.filter(x => !arrB.includes(x));
console.log(difference1, difference1.length);

// Array difference (in B and not in A)
let difference2 = arrB.filter(x => !arrA.includes(x));
console.log(difference2, difference2.length);

// Array symetrical difference
let difference3 = arrA
                 .filter(x => !arrB.includes(x))
                 .concat(arrB.filter(x => !arrA.includes(x)));
console.log(difference3, difference3.length);

// Array union
let union = arrA.concat(arrB);
console.log(union, union.length);