To add months to a JavaScript Date, use the setMonth() method. JavaScript date setMonth() method sets the months for a specified date according to local time.
Example
You can try to run the following code to add 2 months.
<html>
<head>
<title>JavaScript setMonth Method</title>
</head>
<body>
<script>
var dt = new Date("August 20, 2017 11:30:25");
dt.setMonth( dt.getMonth() + 2 );
document.write( dt );
</script>
</body>
</html>