Style fixes here:

```js
var skipLeft = lowerHull[0] === upperHull[0],
    skipRight = lowerHull[lowerHull.length - 1] === upperHull[upperHull.length - 1],
    polygon = [];
```

For that matter you could probably drop "hull" from `lowerHull` and `upperHull` since I think it’s clear enough from the context.