It's funny, I have been using repl.it to test my JS code. The processes using recursion, ES6 or array joins work in repl.it. But, processes using a While (@P1xt example ), or For loops don't work.
For FCC, it's reverse, recursion and ES6 don't work. But, While and For loops do work.
Sometimes, I feel I am coding against FCC tests instead of the best JS coding methods.
I must be doing something wrong, now the recursion and ES6 repeat work in FCC.