Please, help me. I don't understand. Why second solution returns undefined?
function digital_root(n) {
return n < 10 ? n : digital_root(n.toString().split('').map(Number).reduce((a, b) => a + b));
}
console.log(digital_root(12345678));
// expected output: 9
function digital_root(n) {
if (n < 10) {
return n;
} else {
digital_root(n.toString().split('').map(Number).reduce((a, b) => a + b));
}
}
console.log(digital_root(12345678));
// output: undefined
This happens because your second code ignores the value you get returned from the recursive call. You should do something with it... return it.
function digital_root(n) {
if (n < 10) {
return n;
} else {
return digital_root(n.toString().split('').map(Number).reduce((a, b) => a + b));
}
}
console.log(digital_root(12345678));Unrelated, but you can combine split and map by doing Array.from. Also the first version joins the two return statements with the conditional operator into a return of one expression:
const digital_root = n => n < 10 ? n
: digital_root(Array.from(n.toString(), Number).reduce((a, b) => a + b));
console.log(digital_root(12345678));