code: function generateRandomId (length) {
    var str = ''
    length = length || 6
    while (str.length < length) {
      str += (((1 + Math.random()) * 0x10000) | 0).toString(16)
    }
    return str.substring(str.length - length, str.length)
  }
docs: Generate an alphanumeric ID with the given length.
  @param  {Integer} length
  @return {String}        ID