faster, more random, and simpler than the node uuid module. 27 bytes of randomness instead of 16, yet still encoded into a string of length 32

bench.js

var uuid1 = require('uuid');
var crypto = require('crypto');

testOne("uuid module", uuid1);
testOne("my code", uuid2);

function testOne(name, fn) {
  process.stdout.write(name + ": ");
  var start = new Date();
  var s = "";
  for (var i = 0; i < 1000000; i += 1) {
    s += fn();
  }
  var end = new Date();
  console.log((end - start) + "ms");
}

function uuid2() {
  return rando(27).toString('base64');
}

function rando(size) {
  try {
    return crypto.randomBytes(size);
  } catch (err) {
    return crypto.pseudoRandomBytes(size);
  }
}

bench.txt

$ node bench.js 
uuid module: 4362ms
my code: 3202ms


browser: http://jsperf.com/random-string-vs-node-uuid
base64 version is a little slower, but it's also generating 11 more bytes of randomness than uuid v4.

browser.js

var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var crypto = window.crypto;
var arr = new Uint8Array(27);
function uuid() {
  crypto.getRandomValues(arr);
  var s = "";
  for (var m = 0, t = 0; t < arr.length; m = (m + 1) % 4) {
    var x;
    if (m === 0) {
      x = arr[t] >> 2;
      t += 1;
    } else if (m === 1) {
      x = ((0x3 & arr[t-1]) << 4) | (arr[t] >> 4);
    } else if (m === 2) {
      x = ((0xf & arr[t]) << 2) | (arr[t+1] >> 6);
      t += 1;
    } else { // m === 3
      x = arr[t] & 0x3f;
      t += 1;
    }
    s += b64[x];
  }
  return s;
}

uuid.js

var crypto = require('crypto');

module.exports = uuid;

function uuid() {
  return rando(27).toString('base64');
}

function rando(size) {
  try {
    return crypto.randomBytes(size);
  } catch (err) {
    return crypto.pseudoRandomBytes(size);
  }
}