How to make each element of a number array multiply each of its digits within a substring?

Question

I came from Python and am trying to create a function whose goal is to calculate the largest product for a continuous substring of digits of length N. Ex: for the '102181952' input, the largest product for a 3-digit series is 90 (9 * 5 * 2)

I tried to create two loops with for (array[i][j]) equal in Python, but I was unsuccessful. The most I’ve managed so far is to at least create an array of substrings. I tried to use map and reduce, but I was not successful, probably because I do not know how to handle the functions well, although I have read the Documents and researched extensively here in English and Portuguese.

So far what I’ve been able to do, and I don’t think it’ll even do any good was just:

// Ainda não coloquei dentro de uma function(numero, tamanho) 
// para fins de monitoramento.

var numero = '123456789';
var tamanho = 3;
var listaNumeros = [ ];

for (var i = 0; i < numero.length; i += tamanho) {
    listaNumeros.push(numero.substr(i, tamanho));
};

console.log(listaNumeros); // [ '123', '456', '789' ]

Could someone at least point me in the right direction for the solution? I’m simply blank, I can’t think of anything else. Thank you very much!

Answer 1

A path not worrying about validations and this is a minimal example:

var numero = '102181952';
var tamanho = 3;
var listaNumeros = [];

for (var i = 0; i < numero.length; i += tamanho) {
  let s = 1;
  const n = numero.substr(i, tamanho);
  for(var j = 0; j < n.length; j++) {
    s *= parseInt(n[j]);
  }
  listaNumeros.push({n, s});
};

console.log('Resultado:')
console.log(listaNumeros.sort(function(a,b) { return b.s - a.s })[0]);
console.log('Item gerados:')
console.log(listaNumeros);

as wanted the highest value was executed a sort from the largest to the smallest and indicated the first position, as said is a basic example that can help you create a much better example.