Mongoose中Task.update回调的numberAffected与raw参数是否有效？

Great question—this issue boils down to Mongoose version differences that changed the callback signature for update operations. Let's break it down clearly:

Are numberAffected and raw valid parameters? #

They are valid... but only in older Mongoose versions (≤4.x). In Mongoose 5.x and later, the callback structure for update methods was completely revised, which is why you're seeing NaN and undefined in your logs.

What changed between versions? #

• Mongoose ≤4.x: The update() method's callback used three parameters:

  Task.update(filter, update, function(err, numberAffected, rawResponse) {
    // numberAffected = count of documents modified
    // rawResponse = raw MongoDB driver response
  });
  

  If you were using an older version, your code would work as expected.

• Mongoose ≥5.x: The callback now only takes two parameters: err and result. The result is an object containing metadata about the operation, including:

  • n: Number of documents matched
  • nModified: Number of documents actually updated
  • ok: Boolean indicating if the operation succeeded
  • Other driver-specific properties

  Your current code is trying to access numberAffected as the second parameter, which is now the result object—not a number. When you log %d with an object, you get NaN, and the third parameter (raw) doesn't exist anymore, so it's undefined.

Fixing your code #

Update your callback to use the new parameter structure. Here's the corrected version:

var Task = require('../models/task.js');
exports.update = function(req, res) {
  Task.update({ contents : req.body.contents }, { status : req.body.status }, function(err, result) {
    if (err) { throw err; }
    console.log('The number of updated documents was %d', result.nModified);
    console.log('The raw response from MongoDB was', result);
  });
  res.redirect('/');
  res.end();
};

Bonus: Use modern syntax and safer methods #

Mongoose 5.x+ also recommends using updateOne() or updateMany() explicitly (instead of the generic update(), which is an alias for updateMany()) to avoid accidentally updating multiple documents. Here's an async/await version for better readability:

var Task = require('../models/task.js');
exports.update = async function(req, res) {
  try {
    const result = await Task.updateOne(
      { contents : req.body.contents }, 
      { status : req.body.status }
    );
    console.log('The number of updated documents was %d', result.nModified);
    console.log('The raw response from MongoDB was', result);
  } catch (err) {
    console.error(err);
  }
  res.redirect('/');
  res.end();
};

内容的提问来源于stack exchange，提问作者Riddle Aaron