mongodb findOne() 回调 arguments

Question

The official syntax for callback is:
user.findOne({username: "John"}).then((err,doc)=>{}
But this isnt working for me.

Whats working for me is this:
user.findOne({username: "John"}).then((doc,err)=>{}

Any suggestions why is this?

Answer 1

A mongoose query can be executed in one of two ways. First, if you pass in a callback function, Mongoose will execute the query asynchronously and pass the results to the callback.

A query also has a.then() function, and thus can be used as a promise.

1- Here pass error first

Person.findOne({ 'name.last': 'Ghost' }, 'name occupation', function (err, person) {
  if (err) return handleError(err);
  // Prints "Space Ghost is a talk show host".
  console.log('%s %s is a %s.', person.name.first, person.name.last,
    person.occupation);
});

2- Here pass document first

 Band.findOne({name: "Guns N' Roses"}).then(function(doc) { // <- this is the Promise interface.
  // use doc
});

Source: Mongoose documentation