HTML5 Instrumented code with Proxies and the navigation timing API

proxy function

function getInstrumentedFn(fn){
return new Proxy(fn, {
  apply: function(target, that, args){
     //get the function name
     var fName = fn.name || ('random function_' + parseInt(Math.random() * 1000));

     //mark the starting of function.
     performance.mark(fName + '_start');
     var returnValue = fn.apply(that, args);

     //end of the function
     performance.mark(fName + '_end');
     performance.measure(fName + '_performance', fName + '_start', fName + '_end');
     var duration = performance.getEntriesByName(fName + '_performance')[0]['duration'];

     // Add the timing information.
     console.log('The function ' + fName + ' took ' + duration + ' ms');

     return returnValue;
  }
  });
}