docs: function nonce(len) {
    var buf = []
      , chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'
      , charlen = chars.length;
  
    for (var i = 0; i < len; ++i) {
      buf.push(chars[Math.random() * charlen | 0]);
    }
  
    return buf.join('');
  }