To get the number of seconds between two dates, use the Maths.abs() method.
Example
You can try to run the following code to get seconds between two dates −
<html>
<head>
<title>JavaScript Get Seconds</title>
</head>
<body>
<script>
var date1, date2;
date1 = new Date();
document.write(""+date1);
date2 = new Date( "Dec 10, 2015 20:15:10" );
document.write("<br>"+date2);
// get total seconds between two dates
var seconds = Math.abs(date1 - date2) / 1000;
document.write("<br>Difference between 2 dates: "+seconds);
</script>
</body>
</html>Output
Mon May 28 2018 09:35:25 GMT+0530 (India Standard Time) Thu Dec 10 2015 20:15:10 GMT+0530 (India Standard Time) Difference between 2 dates: 77721615.573