221103 Practice

flattenObject.js

const SEP = '.';

/**
 * traversal an object and flatten its nested objects property keys,
 * concatted by a `.` into a single level non-nested object
 * 
 * @param obj object
 * 
 * @returns object
 */
function flattenObject(obj) {
  if (typeof obj !== 'object' || obj === null) {
    return obj;
  }

  const flattened = {};

  for (let key of Object.keys(obj)) {
    const val = obj[key];

    if (typeof val !== 'object' || val === null) {
      flattened[key] = val;
      continue;
    }

    const expanded = flattenObject(val);

    for (let expandedKey of Object.keys(expanded)) {
      flattened[[key, expandedKey].join(SEP)] = expanded[expandedKey];
    }
  }

  return flattened;
}

const testee = {
  str: 'I am string',
  num: 123,
  obj: {
    a: true,
    b: 321,
    c: '',
  },
  obj2: {
    x: 666,
    obj21: {
      i: 'hello',
      j: null,
      k: 999,
      obj211: {
        p: undefined,
        q: 369
      },
      obj212: {
        r: 'world',
        s: 'bye',
      },
    },
    y: 'hi',
    obj22: {
      d: 246,
      obj221: {
        m: 'peace',
        n: 0xFF,
      },
      f: 357,
    },
    z: false,
  },
};

console.log('testee', testee);
console.log('flattenObject(testee)', flattenObject(testee));