add javascript tooltip to existing line chart

Hello again,

Thanks for helping make the tooltip work in the linechart. I am hoping you can show me how to add a ‘box’ outside the tooltip data. I imported the code from online example but no ‘box’ showed up. I attached a picture of what I am looking for with this post. The rest of code is the same as you sent me few days ago.

example: https://bl.ocks.org/Qizly/8f6ba236b79d9bb03a80