Loopback4 and MongoDB query documents with null or undefined field - loopbackjs

Question

How do I query for document with fields that are null or undefined?
e.g.
{id:1, updatedAt: null}
{id:2}
I already tried this code to no avail. Returns 0 matches.
const whereBuilder = new WhereBuilder();
const where: Where = whereBuilder
.eq('updatedAt', null)
//.eq('updatedAt', false)
.build();
myRepository.findOne({
where: where,
});
Thanks for the Help!
Edit 1: Field declaration on model.
#property({
type: 'date',
})
updatedAt?: string;

Answer 1

In MongoDB Shell
using $type operator to match undefined value, see this.
// match `undefined`
db.TEST.findOne({ updatedAt: {'$type':6} });
// match `null`
db.TEST.findOne({ updatedAt: null });
In LB4
// match `undefined`
return await this.myRepository.find(
{
where: {
// !!!! "$" will be added automatically here. (explained below)
updatedAt: { 'type': 6 }
},
}
);
// match `null`
return await this.myRepository.find(
{
where: {
updatedAt: null
},
}
);
Why { 'type': 6 } will be converted into { '$type': 6 } ?
./node_modules/loopback-connector-mongodb/lib/mongodb.js line 918:
your where will be refactored in this function
MongoDB.prototype.buildWhere = function(modelName, where, options) {
...
and in line 1011, { 'type': 6 } will be converted into { '$type': 6 }
...
} else {
query[k] = {};
query[k]['$' + spec] = cond;
}
...
by the way, in line 1016, you can see null will converted as {$type: 10}
...
if (cond === null) {
// http://docs.mongodb.org/manual/reference/operator/query/type/
// Null: 10
query[k] = {$type: 10};
} else {
...