First download momentjs from the link and include this in your html page.
For example:
<head>
<script src="jquery-1.12.0.min.js"></script>
<script type="text/javascript" src="moment.js"></script>
</head>
<body>
Start Date:<div id="startdate"></div>
End Date<div id="enddate"></div>
Week:<div id="weekno"></div>
</body>
<script type="text/javascript">
date = '2015-10-01';
start = moment(date,'YYYY-MM-DD').startOf('week');
//alert(start.format('YYYY-MM-DD HH:mm:ss'));
end = moment(date,'YYYY-MM-DD').endOf('week');
//alert(end.format('YYYY-MM-DD HH:mm:ss'));
week = moment(date,'YYYY-MM-DD').week();
console.log(start);
console.log(end);
$("#startdate").html(start.format('YYYY-MM-DD HH:mm:ss'));
$("#enddate").html(end.format('YYYY-MM-DD HH:mm:ss'));
$("#weekno").html(week);
</script>
For example:
<head>
<script src="jquery-1.12.0.min.js"></script>
<script type="text/javascript" src="moment.js"></script>
</head>
<body>
Start Date:<div id="startdate"></div>
End Date<div id="enddate"></div>
Week:<div id="weekno"></div>
</body>
<script type="text/javascript">
date = '2015-10-01';
start = moment(date,'YYYY-MM-DD').startOf('week');
//alert(start.format('YYYY-MM-DD HH:mm:ss'));
end = moment(date,'YYYY-MM-DD').endOf('week');
//alert(end.format('YYYY-MM-DD HH:mm:ss'));
week = moment(date,'YYYY-MM-DD').week();
console.log(start);
console.log(end);
$("#startdate").html(start.format('YYYY-MM-DD HH:mm:ss'));
$("#enddate").html(end.format('YYYY-MM-DD HH:mm:ss'));
$("#weekno").html(week);
</script>
