Issue with action script


I can not execute the script actions.

   <action-script name="create_agence" model="com.axelor.parametrage.db.Agence">
  <script language="js" transactional="true">
    var hello = $json.create('hello'); = "Hello!!!"; 


I have this error

<action-script name=create_agence>:2:4 Expected an operand but found var var hello = $json.create('hello'); ^ in <action-script name=create_agence> at line number 2 at column number 4


Could you kindly confirm if you have reviewed this with the latest Aos? If you’re still experiencing trouble, we’re here to assist you in solving this issue.

Here is the doc for Script Action Script Action :: Axelor Documentation