JavaScript substring function is used to extract string from string, There are two parameter where first one parameter is start and second one is optional.
<!DOCTYPE html>
<html>
<head>
<title>Welcome to LearnKode - A code learning platform</title>
</head>
<body>
<script>
var anyString = 'Mozilla';
var result= anyString.substring(anyString.length - 4);
document.write(result);
</script>
</body>
</html>
