How to escape special chars in JSON

Both of those are adding extra quotes, just in different ways?

yes and both only work when sending aJSe.

What about ....

bleSendJS(id,aJS);
/* output
_cmd: {"txt":"012345\nabcde\n\u00E4\u00F6\u00FC\u00DF"}
Got:"<- Serial1\r\n>"
Got:"SyntaxError: SyntaxE"
Got:"rror: Expecting a va"
Got:"lid value, got ID\r\n>"
Disconnected
*/
setTimeout(()=>{bleSendJS(id,aJSe);},2E4);
/* output
_cmd: {"txt":"012345\\nabcde\\n\\u00E4\\u00F6\\u00FC\\u00DF"}
Got:"<- Serial1\r\n>"
Got:"SyntaxError: SyntaxE"
Got:"rror: Expecting a va"
Got:"lid value, got ID\r\n>"
Disconnected