Get and use the username of someone who subscribes

I’m trying to check when someone subs

client.on(“subscription”, (channel, username, method, message, userstate) => {
if (self) { return; }
whisperSomeone(username);

and I want to get something like this that i can use in an other part of the code :

${username}

By the way, i am really sorry if it’s confusing, i’m new in development and i try things :frowning: