How to get the next letter of the alphabet in Javascript?

Question

I am build an autocomplete that searches off of a CouchDB View.

I need to be able to take the final character of the input string, and replace the last character wit

Answer 1

my_string.substring(0, my_string.length - 1)
      + String.fromCharCode(my_string.charCodeAt(my_string.length - 1) + 1)