To set the style of the bottom border, use the JavaScript borderBottomStyle property. It allows you to add a bottom border.
Example
You can try to run the following code to set the style of the bottom border −
<!DOCTYPE html>
<html>
<body>
<div id="box">Demo Text</div>
<br>
<button onclick="display()">Click to set style of bottom border</button>
<script>
function display() {
document.getElementById("box").style.borderBottomStyle = "dashed";
}
</script>
</body>
</html>