Js Selector Question

Hi, how are you?

<!-- html -->
<style>
    foo {
        border-right: 1px solid black;
    }
</style>
<div id="foo"></div>

$('#foo').mosedown(function(e) {
    // // event code
}

I want to process the mouse event only on the border-right part when I choose from js.

The entire div tag is processed as a mouse event, so I can't write the code I want

Is there a good way?