How to escape special chars in JSON

I guess there is maybe some problem with how you are sending this? It seems to me from your replace of \ with \ that somehow you're trying to evaluate/parse the string one more times than was intended

Wow - many thanks

code on Puck:

transfer = function (saJS5) {
        var aJS5;
        try {
            aJS5 = eval('('+saJS5+')');
            print("aJS5:",aJS5);
        } catch(e){
            console.log("error in eval:",e);
        }
};

I tried this:

transfer
COMMAND: transfer(""{txt:'012345\\nabcde\\näöüß'}"")  // <- using extra " is the issue

Noble: stateChange -> poweredOn
Found:  Puck.js f5b9
BT> Connecting
BT> Connected
Received "<- Serial1\r\n>"
write: transfer(""{txt:'012345\\nabcde\\näöüß'}"")   

Received "Uncaught SyntaxError"
Received ": Got '{' expected '"
Received ",'\r\n at line 1 col 1"
Received "2\r\ntransfer(\"\"{txt:'"
Received "012345\\\\nabcde\\\\n ?["
Received "228] ?[246] ?[252] ?"
Received "[223]'}\"\")\r\n        "
Received "                    "
Received "       ^\r\n>"
Disconnected

removing the extra " and it works fine

COMMAND: transfer("{txt:'012345\\nabcde\\näöüß'}")

Noble: stateChange -> poweredOn
Found:  Puck.js f5b9
BT> Connecting
BT> Connected
Received "<- Serial1\r\n>"
write: transfer("{txt:'012345\\nabcde\\näöüß'}")

Received "aJS5: { \r\n  \"txt\": \""
Received "012345\\nabcde\\n\\xE4\\"
Received "xF6\\xFC\\xDF\"\r\n }\r\n>"
Disconnected