title: write logs in file using log4js in node js
body: <p>my code is:</p>
  
  <pre><code>log4js.loadAppender('file');
  log4js.addAppender(log4js.appenders.file('logs/cheese.log'), 'cheese');
  logger.setLevel('DEBUG');
  
  logger.trace('Entering cheese testing');
  logger.debug('Got cheese.');
  logger.info('Cheese is Gouda.');
  logger.warn('Cheese is quite smelly.');
  logger.error('Cheese is too ripe!');
  logger.fatal('Cheese was breeding ground for listeria.');
  </code></pre>
  
  <p>it's creating a file named as 'cheese' but nothing is there inside that.
  How to write content in that?</p>