Flat Object

gistfile1.js

const dataSource = {
  one: {
    two: 3,
    four: [5, 6, 7],
  },
  eight: {
    nine: {
      ten: 11,
      eleven: [
        {
          twelve: 13,
        },
      ],
    },
  },
};

function main(obj, parentKey = "") {
  let result = {};

  for (const key in obj) {
    const value = obj[key];
    const newKey = parentKey ? `${parentKey}/${key}` : key;

    if (
      Array.isArray(value) &&
      value.length > 0 &&
      typeof value[0] === "object"
    ) {
      for (let i = 0; i < value.length; i++) {
        const arrayKey = `${newKey}/${i}`;
        Object.assign(result, main(value[i], arrayKey));
      }
    } else if (typeof value === "object") {
      Object.assign(result, main(value, newKey));
    } else {
      result[newKey] = value;
    }
  }

  return result;
}

console.log(main(dataSource));