Poor-man's Javascript performance timing, via http://kellegous.com/j/2013/01/26/layout-performance/

script.js

var Now;
if (typeof performance !== 'undefined' && performance.now) {
  Now = function() {
    return performance.now();
  };
} else if (Date.now) {
  Now = function() {
    return Date.now();
  };
} else {
  Now = function() {
    return new Date().getTime();
  }
}

var Time = function(f) {
  var s = Now();
  f();
  return (Now() - s) | 0;
};

// Useage
var elapsed = Time(function() {
  UpdateNoThrash(data);
});
$('#example-yay-time').text(elapsed + 'ms');