Replace all values of a given key

replaceValues.ts

/**
 * Return a copy of an object, but with values of a key replaced with value of provided key-value object.
 * Useful for duplicating highly nested object, but generating new values for a key (e.g. `id`)
 *
 *
 * @param obj An object
 * @param keyToReplace The key of the values needed to be swapped
 * @param mapOfOldToNewValues A key-value object with a keys of old values mapped to new ones (used for swapping)
 *
 * @example
 * const oldToNewIds = {
 *    'abc': '123',
 *    'xyz': '456'
 * }
 *
 * const initialObj = {
 *   'abc': {
 *      id: 'abc',
 *    },
 *    'xyz': {
 *      id: 'xyz'
 *      parentId: 'abc'
 *    }
 * }
 *
 * console.log(replaceValues(initialObj, 'id', oldToNewIds))
 * ==>
 * {
 *   '123': {
 *      id: '123',
 *    },
 *    '456': {
 *      id: '456'
 *      parentId: '123'
 *    }
 *  }
 */
function replaceValues<T>(
  obj: T,
  keyToReplace: string,
  mapOfOldToNewValues: Record<string, string>
): T {
  // JSON.parse has a second parameter called a reviver that is 
  // a function transforms the results. This function is called 
  // for each member of the object. If a member contains nested
  // objects, the nested objects are transformed before the 
  // parent object is. We can exploit that to deeply transform 
  // any object
  return JSON.parse(JSON.stringify(obj), (key, value) => {
    if (key === keyToReplace && mapOfOldToNewValues.hasOwnProperty(value)) {
      return mapOfOldToNewValues[value];
    }
    return value;
  });
}