Create a JSON like line in CSV with doublequotes

Hello - I am trying to obtain a csv line such as:

"variable_a":"65329845",

But I can’t make it work with the appropriate double-quotes, colon, and double-quotes at the end before the comma.

I tried many things and I am now working on an executeScript_Sandbox approach containing.

var jsonString= 'variable_a' + ${data} + ',';
return jsonString;

if you could share a bit, or all of your Json script so we could understand and help you.