Student.findByIdAndUpdate(helper_id,{$push: {"favour": favour}});
Why can’t the function be executed when I use the above code, but can it be executed when using the following code?
Student.findByIdAndUpdate(helper_id,{$push: {"favour": favour}}).exec()
But why do I use Student.find() and Student.findOne() directly and it can be executed without .exec()?
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
Please refer to Mongoose’s documentation
1. findOneAndUpdate([query], [doc], [options], [callback])
It will only be executed if callback is passed.
2. exec is the way of writing promise, replacing callback, and has the same effect as using callback.
For reference.
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