unsubscribe symbol not working Javascript API

I am unable to unsubscribe symbols using javascript api.

For example:

skt.unsubscribe(['NSE:NIFTY50-INDEX'],false);

console.log(skt.isConnected())

})

It is still streaming 'NSE:NIFTY50-INDEX'.
console error

error in unsubscribe function ReferenceError: logger is not defined