Multiplicative Persistence
const multp = (val, count = 1, res) =>
(res = (val + '').split``
.reduce((a, b) => a * b, 1) + '').length > 1 ?
multp(res, count + 1) : count
console.log('test:', multp(2678789))
Started watching this youtube video from numberphile and instantly made this half-golfed thing
Found this:
f=n=>[n,...n>9?f(eval([...n+''].join`*`)):[]]
By Arnauld over at codegolf.stackexchange
will definitely remember: [...n+'']