Learning jwplayer behavior.

jwplayer_notes.js

jwplayer('player').setup({ ... });

//
// Q: under which conditions does jwplayer return the duration of the current video?
//

console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
"IDLE" -1 // fail

jwplayer('player').play(true)
console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
"PLAYING" 3609.1 // success

jwplayer('player').play(false)
console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
"PAUSED" 3609.1 // success

jwplayer('player').stop()
console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
"IDLE" 3609.1 // success

//
// Q: is this behavior consistent if the player is re-instantiated?
//

jwplayer('player').remove();
jwplayer('player').setup({ ... });
console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
"IDLE" -1 // yes

//
// Q: what event triggers the change?
//

jwplayer('player').onReady(function(){
  console.log("READY", jwplayer('player').getState(), jwplayer('player').getDuration())
})

jwplayer('player').onPlaylist(function(){
  console.log("PLAYLIST", jwplayer('player').getState(), jwplayer('player').getDuration())
})

jwplayer('player').onPlaylistItem(function(){
  console.log("PLAYLIST ITEM", jwplayer('player').getState(), jwplayer('player').getDuration())
})

jwplayer('player').onIdle(function(){
  console.log("IDLE", jwplayer('player').getState(), jwplayer('player').getDuration())
})

jwplayer('player').onPause(function(){
  console.log("PAUSE", jwplayer('player').getState(), jwplayer('player').getDuration())
})

jwplayer('player').onPlay(function(){
  console.log("PLAY", jwplayer('player').getState(), jwplayer('player').getDuration())
})

jwplayer('player').onTime(function(){
  console.log("TIME", jwplayer('player').getState(), jwplayer('player').getDuration())
})

// (reload) ...

READY IDLE -1 // fail
PLAYLIST IDLE -1 // fail
PLAYLIST ITEM IDLE -1 // fail

jwplayer('player').stop() // does not trigger onIdle because already Idle
console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
IDLE -1 // fail

jwplayer('player').play(false) // does not trigger onPause because ???
console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
IDLE -1

jwplayer('player').play(true)
(2 times) PLAY PLAYING -1 // play(true) triggers onPlay, but fails to get duration
(178, etc times) TIME PLAYING 3609.1 // play(true) triggers onTime, and successfully gets duration

jwplayer('player').stop()
IDLE IDLE 3609.1 // .stop() triggers onIdle, and still knows proper duration

//
// Q: how to get video duration as soon as possible?
//

//option A: get within onPlay function?

jwplayer('player').onPlay(function(){
  console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
})

jwplayer('player').play(false)
jwplayer('player').play(true)
PLAYING -1 // (doesn't work; is not an option)
jwplayer('player').play(true)
jwplayer('player').play(false)
jwplayer('player').play(true)
PLAYING 3609.1

// option B: get within onTime function

jwplayer('player').onTime(function(){
  console.log(jwplayer('player').getState(), jwplayer('player').getDuration())
})

jwplayer('player').play(false)
jwplayer('player').play(true)
PLAYING 3609.1 // success

question.js

              jwplayer('player').onTime(function(){

                  // update durationScale based on video duration.

                  var video_duration = this.getDuration(); // #todo: find a way to avoid setting this every iteration of onTime

                  durationScale.domain([0, video_duration]); // #todo: find a way to avoid setting this every iteration of onTime

                  // update current position and reference line based on scaled current position.

                  current_position = this.getPosition();

                  current_position_reference_line.transition()
                      .attr("x1", durationScale(current_position))
                      .attr("x2", durationScale(current_position));

                  var current_progress = current_position / video_duration;
                  var current_progress_percentage = (current_progress * 100).toFixed(5)

                  console.log("POSITION (s):", current_position, "-- COMPLETION (%):", current_progress_percentage); // console.log("STATE:", this.getState()) // this will always log "PLAYING" under the .onTime() function. Time doesn't move when the player is paused.
              });

You can get position and duration from the event object:

 jwplayer('player').onTime(function(e){
    var currentProgress = e.position / e.duration;
    var currentProgressPercentage = e.position * 100 / e.duration;
    console.log('position %ss / duration %ss -- progress %s%', e.position, e.duration, currentProgressPercentage.toFixed());
});

// position 5s / duration 60s -- progress 8.33333%

Thanks @robwalch for that alternate way of accessing duration and position.

My primary question could probably be re-phrased as...

Because the duration stays constant, it doesn't need to be looked up iteratively, right? I'm wondering if there is a way to get duration outside the onTime event, and if this matters with regard to performance.

Yes,

var playerInstance = jwplayer('playerId');
playerInstance.getDuration();
// returns -1 before duration is known
// returns duration after the first time event is processed