title: Please recommend a variable name for the callback function arguments in nodejs, mongodb
body: <p>Since the callback function is overlapped, I don't know how to name variables, <code>err</code> and <code>res</code>.</p>
  <p>Does it matter if all variables have the same name? Is it okay?</p>
  <p>If it's a problem, how do you usually name a variable in such a situation?</p>
  <pre class="lang-js prettyprint-override"><code>app.post('/add', (req, res) =&gt; {
    db.collection('counter').findOne({name: 'numOfPosts'}, (err, res) =&gt; {
      if (err) return console.log(err);
      var count = rep.totalPost;
      db.collection('post').insertOne({id: count + 1, name: req.body.title, date: req.body.date}, (err, res) =&gt; {
        if (err) return console.log(err);
        console.log('저장완료');
        db.collection('counter').updateOne({name: 'numOfPosts'}, {$inc: {totalPost: 1}}, (err, res) =&gt; {
          if (err) return console.log(err);
        });
        res.send('전송완료');
      });
    });
  });
  </code></pre>