I want to print 12321232123..... Like ass infinity in js but I can't get logic so please any one help me on this logic

Question

Get out put as series

Answer 1

1. make a while loop that loops forever. Now inside the loop
2. set a variable, let's say for now `counter` to 1
3. make a for-loop that loops `counter` from 1 till 3, and print each number
4. now make another for-loop that loops `counter` from 3 till 1, and print each number