How to make a specific object from an ordinary object for use in a mongodb $set parameter

How can I transform this object in JavaScript:

let object = {
    a: {
        b: 12
        c: {
           d: 13
        }
    }
}

Into this:

let object = {"a.b": 12, "a.c.d": 13}

I want to modify object and use it like a $set param in mongodb in updateOne method

Use Object.entries to iterate over each [key, value] pair using flatMap, and recursively get to the leaves of the object tree, building up the path to each leaf in the p array. Once a leaf is found, use join to turn the path array into a dotted path string. flatMap is used to ensure that a flat array of [key, value] pairs are returned, instead of a nested array. Finally, we use Object.fromEntries to turn the list of pairs into an array.

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let data = {
  a: {
    b: 12,
    c: {
      d: 13
    }
  },
  e: {
    f: {
      g: 6
    }
  }
}
const f = (v, p=[]) => typeof v === 'object' ? 
  Object.entries(v).flatMap(([k, v]) => f(v, [...p, k])) : [[p.join('.'), v]]
console.log(Object.fromEntries(f(data)))

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