What's wrong with this code?

I have been making a discord.js bot on repl.it, and i want to join an array and then send it into a string.
ac = restofcommand.join("")

Hey! I think that someone here could help you out, but it would probably help to have more information.

What do you want that line to do?
What errors or issues are running into?
Is restofcommand the actual variable you used, or is that a stand-in for you actual code?
What are the contents of the restofcommand variable?
Are you declaring the variable ac, or are you changing it from something else?