I’m not sure how you got to that bit of code, haha! A topic such as this one should have helped.
Assuming the Pastebin content’s syntax is correct for the way you create the array of possible responses, this is how you add such command through the chat:
!addcom can $(eval a = `$(urlfetch json https://pastebin.com/raw/XXXXXXXX)`.split(`;`); '$(query)'.toLowerCase().includes('i join') ? a[Math.floor(Math.random() * a.length)] : ' ';)
Here the command name is “can”, then we check if the message contains “I join” (it doesn’t include the “can” word because that’s the command name), if that’s the case we output a random answer, else we don’t answer.