how to get this month start to end in js code example

Example 1: javascript get current month start and end date

var date = new Date();
var firstDay = new Date(date.getFullYear(), date.getMonth(), 1);
var lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);

Example 2: current month start date and end date with formate in jquery

<html>
   <head>
      <title>JavaScript Dates</title>
   </head>
   <body>
      <script>
         var date = new Date();
         document.write("Current Date: " + date );
         var firstDay = new Date(date.getFullYear(), date.getMonth(), 1);
         document.write("<br>"+firstDay);
         var lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);
         document.write("<br>"+lastDay);
      </script>
   </body>
</html>