How do I get the number of days between two dates in JavaScript? -

how number of days between 2 dates in javascript? example, given 2 dates in input boxes:

<input id="first" value="1/1/2000"/> <input id="second" value="1/1/2001"/>  <script>   alert(datediff("day", first, second)); // goes here? </script> 

function parsedate(str) {      var mdy = str.split('/');      return new date(mdy[2], mdy[0]-1, mdy[1]);  }    function daydiff(first, second) {      return math.round((second-first)/(1000*60*60*24));  }    console.log(daydiff(parsedate($('#first').val()), parsedate($('#second').val())));

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>    <input id="first" value="1/1/2000"/>  <input id="second" value="1/1/2001"/>