我如何使用这个承诺的结果？

Question

I'm trying to build a buildQuery function for my social post feed:

const buildQuery = (criteria) => {
  const { userId, interest } = criteria;
  const query = {};

  if (interest !== 'everything') {
    if (interest === 'myInterests') {
      User.findById(userId).then(user => {
        return query.categories = {
         $in: user.interests
       };
      });
    } else {
      query.categories = { $eq: interest };
    }
  }
  return query;
};

If interest comes through as myInterests then I want to go find the array of interests belonging to the user ( userId ).

Each post has an array of categories: query.categories .

Once I get back the interests array, I want to look up query.categories , to filter down to the posts that the user is interested in myInterests .

Right now, my test is showing that this is just being ignored. It's bringing back all the posts. What am I doing wrong here?

Thank you

Answer 1

You will need to wait for the results, and for that your function needs to return another promise for the updated query.

function buildQuery({userId, interest}) {
  if (interest === 'everything')
    return Promise.resolve({});
  else
    return (interest === 'myInterests'
      ? User.findById(userId).then(user => ({$in: user.interests}))
      : Promise.resolve({$eq: interest})
    ).then(categories => ({categories}));
}

Then wait for this promise before executing the query:

buildQuery(criteria).then(runQuery).then(results => … )