This is not possible. In JSON, there is no error if you use the same name for multiple keys, but the last key with the same name will be used. I suggest using an array for the values for a key.

E.g.:

const res = {
    "a" : {},
    "a" : {}
}

would be

const res = {
    "a" : [{}, {}]
}

Then you could iterate on the list.

if "a" isn't used to identify it's value, it shouldn't be a key. You could restructure you JSON to look like this:

const res = [
  ["a", {}],
  ["a", {}]
]

and then iterate over it using:

for(let [k,v] of res)
  print(k,v)