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In my opinion, the common point here is:

• we just need to care about the values, not keys
• evaluating an object means extracting all the values from it at all deep level then summing up

Assume we need to build a "sum" method, it should:

sum(coolObject) // => 1 + 2 + 3 + 4 + 5 + 6
sum(coolObject.one) // => 1 + 2

Even deeper, for example with:

coolObject.four = {
  number1: 8,
  number2: {
    number21: 7,
    number22: {
      number221: 9
    }
  }
}

sum(coolObject.four) // => 8 + 7 + 9

If you agree with my assumption, what you need may be a single method call that can sum all the values come from any level of the object property. I would like to recommend you to refer my solution as bellow:

let isArray = Array.isArray;
let makeArray = x => Array.from(Object.values(x));

let flatten = (arr) => {
  return arr.reduce((prev, curr) => {
    return prev.concat(isArray(curr) ? flatten(curr) : curr);
  }, []);
};

let decay = (ob) => {
  let arr = makeArray(ob);
  if (arr.length > 0) {
    return arr.map((item) => {
      return decay(item);
    });
  }
  return [ob];
};

let sum = (ob) => {
  let arr = flatten(decay(ob));
  return arr.reduce((prev, curr) => {
    return prev + curr;
  }, 0);
};

With a sum method like that, you can test:

const coolObject = {
  one: {
    number1: 1,
    number2: 2
  },
  two: {
    number1: 3,
    number2: 4
  },
  three: {
    number1: 5,
    number2: 6
  },
  four: {
    number1: 8,
    number2: {
      number21: 7,
      number22: {
        number221: 9
      }
    }
  }
}

console.log(`sum(coolObject.one):`, sum(coolObject.one));
console.log(`sum(coolObject.two):`, sum(coolObject.two));
console.log(`sum(coolObject.three):`, sum(coolObject.three));
console.log(`sum(coolObject.four):`, sum(coolObject.four));
console.log(`sum(coolObject.four.number1):`, sum(coolObject.four.number1));
console.log(`sum(coolObject.four.number2):`, sum(coolObject.four.number2));
console.log(`sum(coolObject):`, sum(coolObject));