Problem passing id-specific objects to javascript via wp_localize_script

In your code playerId is a string. So playerId.tracks can’t work.

So you can create a multidimensional array with wp_localize_script (WP 3.3+):

$playlists = array(
  'playlist150' => array( 'tracks'=> array('track1', 'track2') ),
  'playlist257' => array( 'tracks'=> array('track3', 'track4') )
);
wp_localize_script( 'some_handle', 'allPlaylists', $playlists );

Then in the js use the bracket notation to retrieve the correct array:

jQuery(document).ready(function($) {
  $('.playlist-item').each(function() {
      var tracks = allPlaylists[playerId].tracks // this is an array     
  });
});

---

The previous was a generic information. For what I understand you want to use jPlayerPlaylist object.

What I read in that documantations is it need an instantiation like:

// This is pseudo-code.
var myPlaylist = new jPlayerPlaylist({cssSelector}, , {options});

Where playlist is an array of objects each one is something like:

{
  title:"The Title",
  artist:"The Artist",
  free: true,
  mp3:"http://www.example.com/songs/track1.mp3",
}

and the css selector is an object with two properties, and must me related to div in which the player have to be shown.

Now, if your html containers are:

<div id="playlist150" class="playlist-item"></div>
<div id="playlist257" class="playlist-item"></div>

in a plugin or functions.php you have to create the right arrays, enqueue the scripts and pass the data in a way similar to this:

add_action('wp_enqueue_scripts', 'mytracklists');

function mytracklists() { 
  $playlists = array(
    'playlist150' => array(
      'tracks' => array(
        array(
          'title' => "Track 1",
          'artist' => "One Artist",
          'free' => true,
          'mp3' => "http://www.example.com/songs/track1.mp3",
        ),
        array(
          'title' => "Track 2",
          'artist' => "One Artist",
          'free' => true,
          'mp3' => "http://www.example.com/songs/track2.mp3",
        )
      )
    ),
    'playlist257' => array(
      'tracks' => array(
        array(
          'title' => "Track 3",
          'artist' => "Second Artist",
          'free' => true,
          'mp3' => "http://www.example.com/songs/track3.mp3",
        ),
        array(
          'title' => "Track 4",
          'artist' => "Second Artist",
          'free' => true,
          'mp3' => "http://www.example.com/songs/track4.mp3",
        )
      )
    ),
  );
  wp_register_script('jplayer', get_template_directori_uri() . '/js/jplayer/jquery.jplayer.min.js', array('jquery'));
  wp_register_script('jplayerplaylist', get_template_directori_uri() . '/js/jplayer/add-on/jplayer.playlist.min.js', array('jplayer'));
  wp_enqueue_script('myplaylists', get_template_directori_uri() . '/js//myplaylists.js', array('jplayerplaylist'));
  wp_localize_script( 'myplaylists', 'allPlaylists', $playlists );
}

You see I enqueued jplayer, jplayerplaylist and a custom script called myplaylists that should contain something like:

jQuery(document).ready(function($) {
  // options, valid for all players 
  var my_options = {
    playlistOptions: {
      autoPlay: false,
      loopOnPrevious: false,
      shuffleOnLoop: true,
      enableRemoveControls: false,
      displayTime: 'slow',
      addTime: 'fast',
      removeTime: 'fast',
      shuffleTime: 'slow'
    },
    supplied: "mp3"
  }
  // settings for each player
  $('.playlist-item').each(function() { 
    var cssSelector = {
      jPlayer: '#player_' + $(this).attr('id'),
      cssSelectorAncestor: '#' + $(this).attr('id')
    }
    var playerId = $(this).attr('id');
    // create and populate the playlist array
    // taking data from objet passed via wp_localize_script
    var playlist = new Array();
    $.each( allPlaylists[playerId].tracks, function(i, value) {
      playlist.push(value);
    })
    // instanciate jPlayerPlaylist
    var myPlayer = new jPlayerPlaylist( cssSelector, playlist, my_options );
  });
});

So iterating the div the script create the cssSelector object and create an array of objects containing the tracks. After that use these variable (and the options object) to instanciate the jPlayerPlaylist object.