`childNodes.length` will be falsy for nodes that dont have children

just keep assigning the `lastChild` of `end` to `end` until `end` doesn't have any children. :)

seems straightforward to me but now you've got me wondering what *I* am missing?

I suppose it could also be written
```javascript
while (end.lastChild) {
    end = end.lastChild;
}
```
if thats any clearer?