deepFlatten_improved.js

const obj = {
  A: "12",
  B: 23,
  C: {
    P: 23,
    O: {
      L: 56,
    },
    Q: [1, 2],
  },
  D: null,
  E: {},
  F: [],
};

// Your original version for comparison
let flattenObj = {};

const flatteningObj = (obj, parent) => {
  const keys = Object.keys(obj);
  keys.forEach((key) => {
    const value = obj[key];
    const newParent = parent ? `${parent}.${key}` : key;
    if (typeof value === "object" && value !== null && !Array.isArray(value)) {
      flatteningObj(obj[key], newParent);
    } else if (Array.isArray(value)) {
      value.forEach((item, index) => {
        const arrayKey = `${newParent}.${index}`;
        if (typeof item === "object" && item !== null && !Array.isArray(item)) {
          flatteningObj({ [index]: item }, newParent);
        } else {
          flattenObj = { ...flattenObj, [arrayKey]: item };
        }
      });
    } else {
      flattenObj = { ...flattenObj, [newParent]: value };
    }
  });
};

flatteningObj(obj);
console.log("Your version:", flattenObj);