To set all the border top properties in a single declaration, use the borderTop property. With this property, you can set the border-top-width, border-top-style, and border-top-color property.
Example
You can try to run the following code to learn how to work with border-top properties in JavaScript −
<!DOCTYPE html>
<html>
<head>
<style>
#box {
border: thick solid gray;
width: 300px;
height: 200px
}
</style>
</head>
<body>
<div id="box">Demo Text</div>
<br><br>
<button type="button" onclick="display()">Change top border</button>
<script>
function display() {
document.getElementById("box").style.borderTop = "thick solid #000000";
}
</script>
</body>
</html>