To set the bottom position of a positioned element with JavaScript, use the bottom property.
Example
You can try to run the following code to learn how to set the bottom position −
<!DOCTYPE html>
<html>
<head>
<style>
#newBtn {
position: absolute;
}
</style>
</head>
<body>
<button type="button" id="newBtn" type="button" onclick="display()">Set Bottom Position</button>
<script>
function display() {
document.getElementById("newBtn").style.bottom = "400px";
}
</script>
</body>
</html>