JSFiddle - React, Tailwind, and code Playground

HTML

<div id="left"><a href="#" onclick="document.getElementById('right').innerHTML = (parseInt(document.getElementById('left').innerHTML) + parseInt(document.getElementById('left').innerHTML))">1</a></div>

<div id="right">1</div>

<script type="text/javascript">
    var a = document.getElementById('left').innerHTML;
    
    alert(a);
</script>