I am trying to create mouseover tooltip effects on the graph created by d3. The circle is on top of the line. The problem I meet is that when the mouse is actually on the position of the line, the tooltip is disappeared. Is there a way to ignore the background line?

Mouseover is not triggered because the mouse is pointed at the background line:

[![enter image description here](https://i.stack.imgur.com/LEuZn.jpg)](https://i.stack.imgur.com/LEuZn.jpg)

Mouseover is triggered:
[![enter image description here](https://i.stack.imgur.com/Nxb0e.jpg)](https://i.stack.imgur.com/Nxb0e.jpg)
I have a on mouseover function like this:

```
.on("mouseover", function(thisElement, index){
  //do something when it is selected
})

```