function getIndexToIns(arr, num) {

  var sorted = arr.sort(function(a, b) {
    return a - b;
  });

  var i = 0;
  while (!(num>=sorted[i] && num< sorted[i+1]) ) i++;
  if (num == sorted[i]) return i;
  else return i>=sorted.length ? sorted.length : i+1;

}

getIndexToIns([40, 60], 50);