Mongoose: findOneAndUpdate doesn't return updated document

Below is my code

var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/test');

var Cat = mongoose.model('Cat', {
    name: String,
    age: {type: Number, default: 20},
    create: {type: Date, default: Date.now} 
});

Cat.findOneAndUpdate({age: 17}, {$set:{name:"Naomi"}},function(err, doc){
    if(err){
        console.log("Something wrong when updating data!");
    }

    console.log(doc);
});

I already have some record in my mongo database and I would like to run this code to update name for which age is 17 and then print result out in the end of code.

However, why I still get same result from console(not the modified name) but when I go to mongo db command line and type "db.cats.find();". The result came with modified name.

Then I go back to run this code again and the result is modified.

My question is: If the data was modified, then why I still got original data at first time when console.log it.

Why this happens?

The default is to return the original, unaltered document. If you want the new, updated document to be returned you have to pass an additional argument: an object with the new property set to true.

From the mongoose docs:

Query#findOneAndUpdate

Model.findOneAndUpdate(conditions, update, options, (error, doc) => {
  // error: any errors that occurred
  // doc: the document before updates are applied if `new: false`, or after updates if `new = true`
});

Available options

• new: bool - if true, return the modified document rather than the original. defaults to false (changed in 4.0)

Solution

Pass {new: true} if you want the updated result in the doc variable:

//                                                         V--- THIS WAS ADDED
Cat.findOneAndUpdate({age: 17}, {$set:{name:"Naomi"}}, {new: true}, (err, doc) => {
    if (err) {
        console.log("Something wrong when updating data!");
    }

    console.log(doc);
});