resume-jwplayer.html

<script type="text/javascript">
  var currentPosition = 0;
  if (localStorage.currentPlayerPosition) {
    currentPosition = localStorage.currentPlayerPosition;
  }
  player.once('play', function (){
    'use strict';
    if (currentPosition > 0 && Math.abs(player.getDuration() - currentPosition) > 5) {
      player.seek(currentPosition);		
    }
  })
  window.onunload = function (){
    localStorage.currentPlayerPosition = player.getPosition();
  }
  player.on('error', function (e){
    console.log(e);
    localStorage.currentPlayerPosition = player.getPosition();
    window.localhost.reload(true);
  })
</script>

This assumes your player is loaded to the player variable if it isnt do the following first.

var player = jwplayer();