如何根据数组中的条件从参考数组中提取项目？

Question

I am working in creating a todo list and one of the action I want users to do is delete all completed todos in one click. I have my models here, and the code I have, I have been reading trying to figure it out, but can't find it anywhere. Thanks in advance.

User Model

const UserSchema = new mongoose.Schema({
  name: {
    type: String,
    required: true,
  },
  email: {
    type: String,
    required: true,
    unique: true,
  },
  password: {
    type: String,
    required: true,
  },
  todos: [{
    type: mongoose.Types.ObjectId,
    ref: 'Todo'
  }]
});

Todo model:

const TodoSchema = new mongoose.Schema({
  creator: {
    type: mongoose.Schema.Types.ObjectId,
    required: true,
    ref: 'User',
  },
  content: {
    type: String,
    required: true,
  },
  completed: {
    type: Boolean,
    default: false
  },
});

This is what I have now. I get a "Cast to ObjectId failed for value true at path todos.

router.delete('/delete/completed', auth, async (req, res) => {
  try {
    const userTodos = await User.update(
      {'_id':req.user.id},
      { $pull: {  'todos': { 'completed': true } } },
      { multi: true }
    );

    if (!userTodos) {
      return res.status(400).send('Server error');
    }

    return res.json({ userTodos });
    //return res.json({msg: 'All completed removed'})
  } catch (err) {
    console.error(err.message);
    return res.status(404).json({ msg: 'Something went wrong, try again' });
  }
});

Answer 1

If you are (as it seems from your code) using mongoose, you could use mongoose's populate feature :

const userTodos = await User.find(
  {'_id':req.user.id}).populate('todos', {
    match: {completed: true}
  });

please note, however, that you'll need to delete both the documents in the todos collection, AND the todo reference in the user's todos array. You may consider to remove one side of the reference, see the pros and cons of two-way referencing here