get month start date and end date in javascript

<!DOCTYPE html>
<html>

<head>
        <meta charset="utf-8" />
        <script src="http://code.jquery.com/jquery-2.1.4.min.js"></script>
        <script>
                var nowdate = new Date();
                var monthStartDay = new Date(nowdate.getFullYear(), nowdate.getMonth(), 1);
                var monthEndDay = new Date(nowdate.getFullYear(), nowdate.getMonth() + 1, 0);

                $(function() {
                        $("#StartDate").html(monthStartDay);
                        $("#EndDate").html(monthEndDay);
                });
        </script>
        <style>
                .color{
                        color:green;
                }
        </style>
</head>

<body>
        <h1>get month start date and end date in javascript</h1>
        <div>
                Month StartDate :
                <label id="StartDate" class="color"></label>
        </div>
        <div>
                Month EndDate :
                <label id="EndDate" class="color"></label>
        </div>
</body>

</html>

// Add your javascript here
$(function(){
  $("h1").animate({
    "margin-left": "100px"
  }, "slow");
});

/* Put your css in here */

h1 {
  color: red;
}