x.js

//reset these with every player load/playback session
var PLAY_REACHED_25_PERCENT = false;
var PLAY_REACHED_50_PERCENT = false;
var PLAY_REACHED_75_PERCENT = false;
var PLAY_REACHED_100_PERCENT = false;

kalturaPlayer.addEventListener(kalturaPlayer.Event.Core.TIME_UPDATE, function (event) {
  var progpercent = kalturaPlayer.currentTime / kalturaPlayer.duration;
  if (!PLAY_REACHED_25_PERCENT && progpercent >= 0.25) {
    PLAY_REACHED_25_PERCENT = true;
    console.log("25%");
  }
  if (!PLAY_REACHED_50_PERCENT && progpercent >= 0.5) {
    PLAY_REACHED_50_PERCENT = true;
    console.log("50%");
  }
  if (!PLAY_REACHED_75_PERCENT && progpercent >= 0.75) {
    PLAY_REACHED_75_PERCENT = true;
    console.log("75%");
  }
  if (!PLAY_REACHED_100_PERCENT && progpercent === 1) {
    PLAY_REACHED_100_PERCENT = true;
    console.log("100%");
  }
});