Do you think you could put the body of the function on a new line? Like so:

```
var groupedExamObjs = _.groupBy(examObjs, function (examObj) {
  return examObj.location + examObj.start_date.$date;
});
```

@phleet I checked out the PR locally and the linter does not warn about this line being too long. Does the linter not check for max length of lines?