Conditional deep mapping & deep resolving of Objects.

deep.js

const isObject = 
    obj =>
        obj instanceof Object;

const isPromise =
    obj =>
        typeof obj.then === 'function';

const mapDeepIf =
    (pr, fn, obj) =>
        Object.entries(obj).reduce(
            (copy, [key, value]) =>
                ({
                      ...copy
                    , [key]: isObject(value)
                        ? mapDeepIf(pr, fn, value)
                        : (pr(value)
                            ? fn(value)
                            : value)
                })
            , {}
        );

const resolveAllDeep =
    obj =>
        Object.entries(obj).reduce(
            (copy, [key, value]) =>
                Promise.all([
                      copy
                    , isPromise(value)
                        ? value
                        : (isObject(value)
                            ? resolveAllDeep(value)
                            : Promise.resolve(value))
                ]).then(([copy, value]) =>
                    ({
                          ...copy
                        , [key]: value
                    })
                )
            , Promise.resolve({})
        );

let testObj = {
      a: 1
    , b: 2
    , c: {
          d: 3
        , e: 4
        , f: {
              g: 5
            , h: 6
        }
    }
};

let promiseObj = mapDeepIf(
      x => x > 2 && x < 6
    , x => Promise.resolve(x * 10)
    , testObj
);

resolveAllDeep(promiseObj)
    .then(console.dir.bind(console));