Weird IE, Javascript only works in development mode (F12)

Question

Basically, I have two tags, one is hidden and one is shown.

The hidden one will load video at background, and when the front one is finished, I will swap the two by hiding the shown one.

I will also have a list of playable videos on server side, I will use ajax to get the list and decide which one to load next.

Anyway it is hard for you to try this because you need to have a video server, and I found it's hard to chop the code, so I will just show you the whole source code (with some comments), hope you can understand.

I used jquery and video.js. The source code is as follows,

HTML:

<div class="container" id="video-container-1">
</div>
<div class="container" id="video-container-2">
</div>

Javascript:

//I am making a live video by chopping the video into MP4 files of 800ms each
//The play rate has to be adjustable or the local browser and live server will not sync
var play_rate = { 1.0:800, 1.01:790, 1.02:785, 1.03:777, 1.04:770, 1.05:762, 1.06:755, 1.07:748,
  1.08:741, 1.09:734, 1.1:727 };
var min_rate=1.0;
var max_rate=1.1;
var base_rate = 1.03;
var current_rate = base_rate;
var timer_value = play_rate[current_rate];

var key_to_play;
var timer_id;
var newest_key;
var video_server_address = "192.168.100.1:20001";


var current_play = 1;
var container = new Array();
var player = new Array;

function video_html(container_id, id) {
  return '<video id="video-js-' + container_id + '" class="video-js vjs-default-skin" ' +
  ' preload="auto" width="960" height="540"  crossorigin="anonymous" ' +
  'data-setup=\'{"example_option":true}\'>' +
  '\t<source src="http://' + video_server_address +'/live/' + id + '.mp4" type="video/mp4" /> \n' +
  '\t\t<track id="video-vtt" kind="subtitle" label="english" srclang="en" src="http://' + video_server_address + '/live/' + id + '.vtt" default></track>\n ' +
  '\t\t<p class="vjs-no-js">To view this video please enable JavaScript, and consider upgrading to a web browser that <a href="http://videojs.com/html5-video-support/" target="_blank">supports HTML5 video</a></p>\n' +
  '</video>';
}
function play_next()
{
  var next_play;
  if (current_play == 1)
    next_play = 2;
  else
    next_play = 1;

  player[next_play - 1].play();
  container[next_play - 1].show();
  container[current_play - 1].hide();
  if (player[current_play - 1])
    player[current_play - 1].dispose();

  key_to_play++;

  //switch current & next
  current_play = next_play;

  timer_id = setTimeout(function() {
    play_next();
  }, timer_value);

  //Assuming get list + load video < 700ms
  $.get("http://" + video_server_address + "/live/list", 
    function(list){
      keys = list["keys"];
      newest_key = keys[keys.length - 1];


      console.log("key_to_play: " + key_to_play + "  newest_key: " + newest_key);

      var next_play;
      if (current_play == 1)
        next_play = 2;
      else
        next_play = 1;
      //-----------------begin-------------------
      //not really useful to you because these are just 
      //to let the video play sync with video server, we can safely 
      //remove these but the video play will out of sync after some time    
      if (key_to_play > newest_key)
      {
        //too fast
        //make it slower?
        if (current_rate > min_rate)
        {
          current_rate = current_rate - 0.01;
          timer_value = play_rate[current_rate];
        }
        else
        {
          //it is already 1.0 (the slowest settings)
          //have to crop on the timer_value
          timer_value = play_rate[current_rate] + 5 * (key_to_play - newest_key);
        }
        //either wait or play again? just play again and test for stability first
        key_to_play = newest_key;
      }
      else if (key_to_play == newest_key || key_to_play == newest_key - 1)
      {
        //the best situation we got
        //don't change anything
      }
      else
      {
        //a little slow
        if (current_rate < max_rate)
        {
          current_rate = current_rate + 0.01;
          timer_value = play_rate[current_rate];
        }
        else
        {
          timer_value = play_rate[current_rate] - 5 * (newest_key - key_to_play);
        }

        //tooo slow, drop 4 * 800ms data
        if (newest_key - key_to_play > 5)
        {
          key_to_play = newest_key - 1;
        }
      }
      //-------------------end------------

      container[next_play - 1].html(video_html(next_play, key_to_play));
      player[next_play - 1] = videojs('video-js-' + next_play, {}, function(){
        // Player (this) is initialized and ready.
        //the following is only to make the browser show subtitle
        //without this, the FF will not show subtitle by default
        $('#video-container-' + next_play + " div.vjs-subtitles-button li.vjs-menu-item").eq(1).trigger('click');
      });
      player[next_play - 1].playbackRate(current_rate);



      console.log(timer_value);
    }
  );



}

$( document ).ready(function() {
  $.get("http://" + video_server_address + "/live/list", function(list){
    keys = list["keys"];
    key_to_play = keys[keys.length - 2];
    newest_key = keys[keys.length - 1];

    container[0] = $("div#video-container-1");
    container[1] = $("div#video-container-2");
    container[0].hide();

    container[1].html(video_html(2, key_to_play));
    player[0] = null;
    player[1] = videojs("video-js-2",{}, function(){
      // Player (this) is initialized and ready.
      console.log($("#video-container-2 div.vjs-subtitles-button li.vjs-menu-item").eq(1).text());
      $("#video-container-2 div.vjs-subtitles-button li.vjs-menu-item").eq(1).trigger('click');
    });
    player[1].playbackRate(current_rate);

    play_next();
  });
});
</script>

This code works good on chrome and FF, however, when trying on IE11, the new videos will not load, it will switch between two videos (say video 1 and 2) every 800ms, and I think it will load the latter ones (3, 4, 5 and so one), but it will not play, it is just keep playing 1 and 2 and 1 and 2.

When I try to debug it, I open IE11 development tools, then when development tools is ready, IE11 will work well.

As long as I close the development tools, IE11 will suck.

I am thinking maybe IE11 made some optimization and optimized some of the codes away? How can I check that?

Thanks.

Answer 1

Taken from the comments on the original question:

Why does JavaScript only work after opening developer tools in IE once?

For OP it was the caching of his Ajax request causing the issue. Solved by disabling the cache:

$.ajax({cache: false, ...})

Answer 2

As you are using the below code

console.log("key_to_play: " + key_to_play + "  newest_key: " + newest_key);

Here you should check if the console object exists or not, when you press F12, it automatically creates console object, you should write it like this

if (typeof console == "object") {
    console.log("key_to_play: " + key_to_play + "  newest_key: " + newest_key);
}
else{
    //do nothing`enter code here`
}