Flatten object with paths

flattenObject.js

const flattenObject = (value, key = null, flattenedObject = {}) => {
  if (
    ['string', 'number', 'bigint', 'boolean', 'undefined', 'symbol'].includes(typeof value) ||
    value === null ||
    value instanceof Date
  ) {
    flattenedObject[key] = value;
  } else if (Array.isArray(value)) {
    value.forEach((childValue, childIndex) => {
      flattenObject(childValue, `${key}[${childIndex}]`, flattenedObject);
    });
  } else if (typeof value === 'object') {
    let computedKey;
    for (const childKey in value) {
      computedKey = (typeof key === 'string' ? key + '.' : '') + childKey;
      flattenObject(value[childKey], computedKey, flattenedObject);
    }
  }
  return flattenedObject;
};

Use case:

const data = {
  name: 'name',
  id: Symbol('id'),
  date: new Date(),
  nullable: null,
  notDefined: undefined,
  __meta__: {
    tags: ['tag1', 'tag2', 'tag3'],
    maxSafeInteger: BigInt(Number.MAX_SAFE_INTEGER)
  }
};

flattenObject(data);

Result:

{
  name: 'name',
  id: Symbol(id),
  date: 2021-03-06T18:34:51.813Z,
  nullable: null,
  notDefined: undefined,
  '__meta__.tags[0]': 'tag1',
  '__meta__.tags[1]': 'tag2',
  '__meta__.tags[2]': 'tag3',
  '__meta__.maxSafeInteger': 9007199254740991n
}