code: function logger(level) {
    var args = slice.call(arguments, 1);
  
    if (typeof args[0] !== 'string') args.unshift('');
  
    level = logger.levels[level];
  
    args[0] = '\x1b['
      + level[0]
      + 'm['
      + logger.prefix
      + ']\x1b[m '
      + args[0];
  
    if ((level[1] === 'log' && !logger.isatty[1])
        || (level[1] === 'error' && !logger.isatty[2])) {
      args[0] = args[0].replace(/\x1b\[(?:\d+(?:;\d+)*)?m/g, '');
    }
  
    return console[level[1]].apply(console, args);
  }
docs: Logger