[Scripting] application/x-www-form-urlencoded body is wrong when using Script

Description

application/x-www-form-urlencoded body is wrong when using Script

Steps to Reproduce

1. Make this cURL

curl -X POST 'https://httpbin.proxyman.app/post' \
  -H 'Content-Type: application/x-www-form-urlencoded' \
  --data-urlencode 'field01=value01' \
  --data-urlencode 'field02=value02' \
  --data-urlencode 'field03=value03' \
  --data-urlencode 'field04=value04' \
  --data-urlencode 'field05=value05' \
  --data-urlencode 'field06=value06' \
  --data-urlencode 'field07=value07' \
  --data-urlencode 'field08=value08' \
  --data-urlencode 'field09=value09' \
  --data-urlencode 'field10=value10' \
  --data-urlencode 'field11=value11' \
  --data-urlencode 'field12=value12' \
  --data-urlencode 'field13=value13' \
  --data-urlencode 'field14=value14' \
  --data-urlencode 'field02=value15' \
  --data-urlencode 'field16=value16' \
  --data-urlencode 'field17=value17' \
  --data-urlencode 'field18=value18' \
  --data-urlencode 'field19=value19' \
  --data-urlencode 'field20=value20' --proxy localhost:9090

2. Make new Script with this content:

async function onRequest(context, url, request) {
  // console.log(request);
  console.log(url);

  var body = request.body;
  body["new_key"] = "new value"
  request.body = body;

  // Done
  return request;
}

3. Verify the Form body

Current Behavior

• Duplicated keys has a [], which is incorrect
  

Expected Behavior

• Should not contain the []

Environment

• App version: e.g Proxyman 5.23.1