JSFiddle - React, Tailwind, and code Playground

HTML

<a href="#">link1</a>
<a href="#">link2</a>
<a href="#">link3</a>
<a href="#">link4</a>
<a href="#">link5</a>
<a href="#">link6</a>
<a href="#">link7</a>
<a href="#">link8</a>
<a href="#">link9</a>
<a href="#">link10</a>

JavaScript

var links = document.getElementsByTagName('a')
for (var i=0; i<links.length; i++) {
    (function(i){
        links[i].onmouseover = function(){
            alert(i)
        }
    })(i)
}