// @license http://opensource.org/licenses/MIT
// copyright Paul Irish 2015


// Date.now() is supported everywhere except IE8. For IE8 we use the Date.now polyfill
//   github.com/Financial-Times/polyfill-service/blob/master/polyfills/Date.now/polyfill.js
// as Safari 6 doesn't have support for NavigationTiming, we use a Date.now() timestamp for relative values

// if you want values similar to what you'd get with real perf.now, place this towards the head of the page
// but in reality, you're just getting the delta between now() calls, so it's not terribly important where it's placed


(function(){

    if ("performance" in globalThis == false) {
        globalThis.performance = {};
    }
    
    Date.now = (Date.now || function () {  // thanks IE8
        return new Date().getTime();
    });
  
    if ("now" in globalThis.performance == false){
      
      var nowOffset = Date.now();
      
      if (performance.timing && performance.timing.navigationStart){
        nowOffset = performance.timing.navigationStart
      }
  
      globalThis.performance.now = function now(){
        return Date.now() - nowOffset;
      }
    }
  
  })();