<div>
Lorem Ipsum is simply
dummy text of the printing
and typesetting industry.
</div>
<div>
Lorem Ipsum is simply
dummy text of the printing
and typesetting industry.
</div>
<style>
span {
display: inline-block;
background: deeppink;
margin: 1em;
padding: 1em;
}
</style>
<script>
document.querySelectorAll("div").forEach(node => node.innerHTML = node.innerHTML.replace(/(.+)\r?\n/g, '<span>$1</span>'));
</script>
Вариант
