Hello,

Arguments Optional

In the FCC solution 1:

```
function addTogether() {
const [first, second] = arguments;
// First argument is not a number
if (typeof(first) !== "number") {
return undefined;
}
// First argument is a number
// and second argument is not defined
else if (second === undefined) {
function addSecond(second) {
// New argument is not a number
if (typeof(second) !== "number") {
return undefined;
}
// New argument is a number
else {
return first + second;
}
}
// Note: returning a *function*
return addSecond;
}
// First argument is a number
// and second argument is not a number
else if (typeof(second) !== "number") {
return undefined;
}
// First argument is a number
// and second argument is a number
else {
return first + second;
}
}
console.log(addTogether("https://www.youtube.com/watch?v=dQw4w9WgXcQ"))
```

In ` else if (second === undefined) {`

section,

I don’t understand this part:

```
// New argument is a number
else {
return first + second;
}
```

How “second” could be a number since `(second === undefined)`

?