indexes.js

/*
  @arr: array of 0s and 1s
  @returns: an array of indexes
*/
const findIndexes = arr => {
  return arr.reduce((m, e, i) => {
    e && m.push(i)
    return m
  }, [])
}

/*
  @arr: array of 0s and 1s
  @returns: an index of the number 1 or undefined
*/
const findIndex = arr => {
  return arr.findIndex(x => x == 1)
}