JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <input type="checkbox" id="cb1" />
    <input type="checkbox" id="cb2" />
    <input type="checkbox" id="cb3" />
    <input type="checkbox" id="cb4" />
</div>

JavaScript

function analyze_checkbox(cb) { 
 alert(cb.index());
}

$(function(){
    analyze_checkbox( $('#cb3') );
    });