Problem

Given an object with nested objects, write a function that flattens the object.
Input:
{
  "a": 1,
  "b": {
    "c": 2,
    "d": {
      "e": 3
    }
  }
}
Output:
{
  "a": 1,
  "b.c": 2,
  "b.d.e": 3
}

Solution

function flattenObject(obj) {
  let result = {};
  for (let key in obj) {
    if (typeof obj[key] === "object") {
      let flatObject = flattenObject(obj[key]);
      for (let flatKey in flatObject) {
        result[key + "." + flatKey] = flatObject[flatKey];
      }
    } else {
      result[key] = obj[key];
    }
  }
  return result;
}

// This solution is optimal because it is recursive and will work for any number of nested objects.