JWPlayer setup() is it mandatory to have it before listening to player events ?

Hi , I am embedding jwplayer in my html page . The jwplayer.on() listeners is behaving differently in google chrome and MAC Safari . In google chrome the jwplayer().on("playlistItem", function() listener if called before jwplayer().setup() works fine . if the same html page loaded on safari is throwing TypeError: jwplayer().on is not a function. (In 'jwplayer().on', 'jwplayer().on' is undefined) when i added jwplayer().setup() just before jwplayer().on("playlistItem", function() it worked in both chrome and safari . The question is , is it mandatory to have jwplayer().setup() before the listening to the player events ? If so why it is working in google chrome and not in safari ? Thanks