Use the textDecoration property in JavaScript to decorate the text. You can underline a text using this property.
Example
You can try to run the following code to set the decoration of a text with JavaScript −
<!DOCTYPE html>
<html>
<body>
<div id = "myText">This is demo text.</div><br>
<button onclick = "display()">Set Text Decoration</button>
<script>
function display() {
document.getElementById("myText").style.textDecoration = "underline";
}
</script>
</body>
</html>