Trying to get full video duration but returning as Nan

Wait for onloadedmetadata event, The loadedmetadata event is fired when the metadata has been loaded.

var myVideo = document.getElementById("videoPlayerNew");
myVideo.onloadedmetadata = function() {
  console.log('metadata loaded!');
  console.log(this.duration);//this refers to myVideo
};
<video id="videoPlayerNew" class="video-js vjs-default-skin vjs-controls-enabled" poster="http://camendesign.com/code/video_for_everybody/poster.jpg" data-setup="{}" controls="">
  <source src="http://www.w3schools.com/html/mov_bbb.mp4" type="video/mp4">
    <p class="vjs-no-js">Javascript was disabled or not supported</p>
</video>

Try this code below, it adds the event after everything is loaded :

$(document).ready(function(){
  $("#videoPlayerNew").on( "timeupdate", function(event){
      console.log( this.duration);
    });
});