I have a JSON object which is

```
let data = {
 "key1" : 1,
 "key2" : 2,
 "subKeys":{
  "subKey1" : 3,
  "subKey2" : 4
  }
}

```

I want my resultant JSON like this structure:

```
let resultantData = {
 "key1":1,
 "key2":2,
 "subKey1":3,
 "subKey2":4
}

```

How can I achieve this goal