function addAndAdd(number) {
number = Number(number)
if (isNaN(number)) {
return '0'
} else if (0===number) {
return '5'
}
const string = number + ''
if (1===string.length) {
return string
}
let sum = 0
for (let i=0; i<string.length; i++) {
sum += Number(string[i])
}
return addAndAdd(sum)
}