JS Script generate valid string

I need a script can generate two types of valid string First Example: AAAA10 Second Example: AA0100 The script should be able to generate correlative strings start of First type: AAAA10 Output example: AAAA10, AAAA11, AAAA12 ... AAAA99, AAAB10 ... AAAB99, AAAC10 When the correlative get to 99 the last char must be change to the next char in the alphabet The end of the first example must be ZZZZ99 Second type: AA0100 Output example: AA0100, AA0101, AA0102 ... AA9999, AB0100 ... AB9999, AC0100 When the correlative get to 9999 the last char must be change to the next char in the alphabet and the number must be start 0100 The end of the first example must be ZZ9999 First and second type must be a separate functions, and each one need "save the progress" of the last valid string (can be a txt) because i use this string in a async function, if i stop the process, the script read the last valid string generate and start with that in the new execution. The script must be with the syntax of ECMAScript 6