Generate V4 UUIDs in node.js

uuid.js

function uuid() {
  var bytes = require('crypto').randomBytes(16);
  bytes[6] = (bytes[6] & 0x0f) | 0x40;
  bytes[8] = (bytes[8] & 0x3f) | 0x80;
  var str = bytes.toString('hex');
  return str.substr(0,  8) + '-' +
         str.substr(8,  4) + '-' +
         str.substr(12, 4) + '-' +
         str.substr(16, 4) + '-' +
         str.substr(20, 12);
}