Everything works fine now following your example.
Thank you very much for your kind support!

This is the minimal template, very similar to your example but just adding some ifs.

https://playground.jsreport.net/studio/workspace/HkLP_eNqM/2

Perhaps your example works fine from API because there is sample data defined.

Your solution is very close, containing already that what i need!

<script>
    var dataEl = document.getElementById('data-serialized')
    var data = JSON.parse(dataEl.innerText);
</script>

But there is still an issue.
If i call the template containing this

    <script>
        var dataEl = document.getElementById('data-serialized')
        
        if(dataEl === undefined)
        {
            document.write("dataEl is undefined");
        }
        
        if(dataEl === null)
        {
            document.write("dataEl is null");
        }
    </script>

over API, the document shows 'dataEl is null'.
What is happening now?

Exactly, i want to access the data in the template.
I just viewed 'Deep dive into jsreport' on YouTube.
Is this the right approach?

    <script>
        var data = [];
        
        data.push({{Message}});
    </script>

Hi all,

we are just starting with jsreport and facing a problem now.
Currently we are loading (test) data from a local JSON file.
In the next step we like to call the API for the report to be rendered.
Imagine the following body in the API call.

   { 
      "template": { "shortid" : "g1PyBkARK"  },
      "data" : { "Message" : "Hello World!" },
      "options": { "timeout": 60000 }
   }

How can we access the 'data' as a JavaScript object within the report Definition?

Perhaps you can give a link or a short code snippet.

Best regards
Dirk