// https://www.freecodecamp.org/learn/coding-interview-prep/data-structures/perform-a-union-on-two-sets

class Set {
  constructor() {
    // This will hold the set
    this.dictionary = {};
    this.length = 0;
  }
  // This method will check for the presence of an element and return true or false
  has(element) {
    return this.dictionary[element] !== undefined;
  }
  // This method will return all the values in the set
  values() {
    return Object.values(this.dictionary);
  }
  // This method will add an element to the set
  add(element) {
    if (!this.has(element)) {
      this.dictionary[element] = element;
      this.length++;
      return true;
    }

    return false;
  }
  // This method will remove an element from a set
  remove(element) {
    if (this.has(element)) {
      delete this.dictionary[element];
      this.length--;
      return true;
    }

    return false;
  }
  // This method will return the size of the set
  size() {
    return this.length;
  }
  // Only change code below this line
  union(otherSet) {
    const unionSet = new Set();
    for (let set of [this, otherSet]) {
      for (let key in set.dictionary) {
        unionSet.add(key);
      }
    }
    return unionSet;
  }
  // Only change code above this line
}

const setA = new Set();
for (let element of ["a", "b", "c"]) {
  setA.add(element);
}
const setB = new Set();
setB.add("c");
setB.add("d");

console.log(setA.union(setB));