Do anyone understand this reduce method problem Im having?

Do anyone understand why console.log(posArr) is printing [1,2,3] and not [0,1,2]. Im trying to push to nOfPos all the index positions of my array 🙂

function combinations(x) {
  let arr = x.toString().split('');
  console.log(arr)

  let nOfPos = [];
  let posArr = arr.map(x => nOfPos.push(arr.indexOf(arr[x])));
  let mult = posArr.reduce((acum, item) => acum * item);

  console.log(posArr);
  console.log(mult);
}

combinations(123)

>Solution :

The problem is due to two errors in your code. Firstly push() returns the new length of the array, so that’s why the mapped output contains the incremental 1,2,3....

Secondly, you need to search for x within arr, so you only need to pass x to indexOf().

With those issues corrected the code works:

function combinations(x) {
  let arr = x.toString().split('');
  let posArr = arr.map(x => arr.indexOf(x));
  let mult = posArr.reduce((acum, item) => acum * item);

  console.log(posArr);
  console.log(mult);
}

combinations(123)

That being said, the purpose of posArr is a little redundant; it will always be an array of incremental values, up to the length of the string -1.

In addition, mult is redundant too as it will always be 0, as you are multiplying by 0.