phpjs/functions/datetime/microtime.js

php.js offers community built php functions in javascript

function microtime(get_as_float) {
  // From: http://phpjs.org/functions
  // +   original by: Paulo Freitas
  // *     example 1: timeStamp = microtime(true);
  // *     example 1: timeStamp > 1000000000 && timeStamp < 2000000000
  // *     returns 1: true
  var now = new Date().getTime() / 1000;
  var s = parseInt(now, 10);

  return (get_as_float) ? now : (Math.round((now - s) * 1000) / 1000) + ' ' + s;
}