persistant-bugger.js

// Write a function, persistence, that takes in a positive parameter num and returns its multiplicative persistence, which is the number of times you must multiply the digits in num until you reach a single digit.

// For example (Input --> Output):

// 39 --> 3 (because 3*9 = 27, 2*7 = 14, 1*4 = 4 and 4 has only one digit)
// 999 --> 4 (because 9*9*9 = 729, 7*2*9 = 126, 1*2*6 = 12, and finally 1*2 = 2)
// 4 --> 0 (because 4 is already a one-digit number)

//solution


function persistence(num) {
    const str = num.toString();
    if (str.length === 1) {
      return 0;
    }
    const nextNum = str.split('').reduce((a, b) => a * b, 1);
    return 1 + persistence(nextNum);
  }

//learnt alot about recursive functions!