Untitled

<!DOCTYPE HTML>
<html>
<head>
    <meta charset="utf-8">
    <title>parentNode</title>
</head>
<body>
<ul>
    <li>text</li>
    <li>text</li>
    <li id="elem">text</li>
    <li>text</li>
    <li>text</li>
</ul>
<script>
    let elem = document.querySelector('#elem');
    let text = elem.previousElementSibling.innerHTML;
    text.addEventListener('click',function(){
        text.innerHTML=text.innerHTML+'!';
    })


</script>
</body>
</html>