Translating DOMTimeStamp to DOMHighResTimeStamp

translate-timestamp.js

// Translate Event.timeStamp to a DOMHighResTimeStamp that can be compare with
// performance.now(). this becomes a no-op for browsers that provide 
// high resolution event timestamp.
toHighResTimeStamp = (function(testTimeStamp){
  function timeNear(a, b) {
    var d = 1000 * 60 * 5;
    return a > b - d && a < b + d;
  }

  var timebaseDelta_ = 0;
  
  // Detect if this browser is using DOMTimeStamp and adjust timebase if needed. 
  if (timeNear(testTimeStamp, Date.now())) {
    // Delta is the difference between current time is both timebases.
    timebaseDelta_ = Math.round(performance.now() - Date.now());
  }

  return function(timeStamp) {
    return timeStamp + timebaseDelta_;
  }
}(new Event('test').timeStamp));

// Usage example:
// var latency = performance.now() - toHighResTimeStamp(e.timeStamp);