**Tell us what’s happening:**

Error shows: addTogether(…) is not a function.

I make the spread array items as the parameters which I used many times before but now throws an error.

Thank guys very much for your answers.

**Your code so far**

```
function addTogether(...num) {
if (num.length === 1) {
if (typeof num !== 'number') {
return undefined;
} else {
return num2 => typeof num2 !== 'number'? undefined: num + num2;
}
} else {
for (let item of num) {
if (typeof item !== 'number') {
return undefined;
}
}
return num.reduce((a, b) => a + b);
}
}
console.log(addTogether(2, 3));
```

**Your browser information:**

User Agent is: `Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36`

.

**Link to the challenge:**

https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/arguments-optional