I have this set to a form text box field “email” I am trying to embed this userid to split the 

jon.doe   from   email john.doe@domain.com

so that userid = jon.doe

Using the below

Qualtrics.SurveyEngine.addOnUnload(function()
{
    var email = "${q://QID48/ChoiceTextEntryValue/1}}";
    var substrings = email.split("@", 2);
    var userID = substringsI0];
    
    
    // Set the user ID as embedded data
    Qualtrics.SurveyEngine.setEmbeddedData("userID", userID);

It's not working. Please help, thx