Unexpected Token Else


So i’ve been learning javascript in class and was given a task to create a short program that determines whether a number is a ISBN or not.
I created my program however when i attempt to run it it logs that i have an unexpected token else in the console. Can anyone please look at my code and help me fix my code
Many thanks!

Code: https://repl.it/@Illflame01/PoisedUnitedComputing


check your curly brackets, where do you close/end your function?