the problem with this is for very large denominators, the while loop will also execute for a large number of times. it's better to have a GCF function instead

i don't get why this is considered as a best practice. the code is very hard to read; please use descriptive yet short variable names next time. you can get a cleaner solution also by using a recursion, which i consider is better than having so much nested loops. check my solution

you can take the vars outside of the function so that it wont be recreated every step of the recursion

you can use toString().length to get the number of digits instead of looping. Or better, toString().split("") and then get the length while also getting the digits individually