2722-join-two-arrays-by-id.js

/**
 * 2722. Join Two Arrays by ID
 * https://leetcode.com/problems/join-two-arrays-by-id/
 * Difficulty: Medium
 *
 * Given two arrays arr1 and arr2, return a new array joinedArray. All the objects in each
 * of the two inputs arrays will contain an id field that has an integer value.
 *
 * joinedArray is an array formed by merging arr1 and arr2 based on their id key. The length
 * of joinedArray should be the length of unique values of id. The returned array should be
 * sorted in ascending order based on the id key.
 *
 * If a given id exists in one array but not the other, the single object with that id should
 * be included in the result array without modification.
 *
 * If two objects share an id, their properties should be merged into a single object:
 * - If a key only exists in one object, that single key-value pair should be included in
 *   the object.
 * - If a key is included in both objects, the value in the object from arr2 should override
 *   the value from arr1.
 */

/**
 * @param {Array} arr1
 * @param {Array} arr2
 * @return {Array}
 */
var join = function(arr1, arr2) {
  const map = new Map();
  [...arr1, ...arr2].forEach(obj => map.set(obj.id, { ...map.get(obj.id), ...obj }));
  return Array.from(map.values()).sort((a, b) => a.id - b.id);
};