A simple function to test performance.

benchmark.js

/**
 * A simple function to test performance.
 */
function benchmark() {
  var tests = Array.prototype.slice.call(arguments);
  var length = tests.length;
  var startTimes = Array(length);
  var result = Array(length);
  
  var times = typeof benchmark.times === 'number' ? benchmark.times/2 : 5000;

  for (var i = 0; i < length; i++) {
    startTimes[i] = new Date();
    for (var j = 0; j < times; j++) {
      tests[i]();
    }
    result[i] = new Date() - startTimes[i];
  }
  
  for (i = length - 1; i >=0; i--) {
    startTimes[i] = new Date();
    for (var j = 0; j < times; j++) {
      tests[i]();
    }
    result[i] += new Date() - startTimes[i];
  }
  
  return result;
}