How about:

```
var tipContentHTML = graph.options.tooltip.formatter(graph.tooltips[index], graph.options.messages),
    $toolTipContent = graph.$tooltip.find('.elroi-tooltip-content').html(tipContentHTML),
    $toolTipContainer = $toolTipContent.find('.elroi-tooltip-container');
```

A couple things to note here:
1) If a `var` is a jQuery object, prefix it with `$`.  Make sure to fix the boolean logic below `if($toolTipContainer && $toolTipContainer...`
2) It was a bit unclear to me what the difference between `tipContent` and `toolTipContent` was at first glance.  I think by renaming `tipContentHTML` it makes it more obvious and with that I'd be comfortable dropping the multiline comment.