How to use script_fields and script_score in a simple query (search)

[Eli-Goldberg]

I have the following query (below), but I can't figure out how to do that in the JS client.
I couldn't find both script_score (1) inside the query, but also script_fields (2) inside the body.

Is this supported in the client?

GET test-index/_search
{
  "query": {
    "function_score": {
      "query": {
        "range": {
          "value": { "lte": 20 }
        }
      },
      "script_score": { <-- (1)
        "script": { "source": "doc['value'].value < 21 ? 1 : 0" }
      }
    }
  },
  "script_fields": { <-- (2)
    "value_below_21": {
      "script": { "inline": "return doc['value'].value < 21 ? 1 : 0" }
    }
  }
}

[stale]

We understand that this might be important for you, but this issue has been automatically marked as stale because it has not had recent activity either from our end or yours.
It will be closed if no further activity occurs, please write a comment if you would like to keep this going.

Note: in the past months we have built a new client, that has just landed in master. If you want to open an issue or a pr for the legacy client, you should do that in https://github.com/elastic/elasticsearch-js-legacy