Mongodb - remove null fields "recursively"? - mongodb

Question

This is a question based on MongoDb - remove all fields that are null. The referred post only gives solution that removes null fields at the top level. However, how can I remove the null fields that embedded?
Please note that I have no idea of the possible names of the null fields and their depth, so I think we have to iterate over each field of each document.
This is an example:
{
"id": 14770467,
"f1": "a",
"f2": null,
"f3": [
{
"id": 76946819,
"f4": null
}
]
}
I'm expecting something like this:
{
"id": 14770467,
"f1": "a",
"f3": [
{
"id": 76946819
}
]
}
Thanks.

Answer 1

try this
const remove = (data) => {
for (let key in data) {
const val = data[key];
if (val == null) {
delete data[key];
} else if (Array.isArray(val)) {
val.forEach((v) => {
remove(v);
});
}
}
return data;
}
db.getCollection('Collection').find({}).forEach((data) => {
data = remove(data);
db.getCollection('OtherCollection').insert(data);
//db.getCollection('Collection').save(data); // update same record
print(data);
})

Answer 2

Above was not working for me. But was inspiration to seek for more.
This worked (with MongoDB shell version v4.0.5):
const remove= (obj) => {
Object.keys(obj).forEach(key => {
if (obj[key] && typeof obj[key] === 'object') removeEmpty(obj[key]);
else if (obj[key] == null) delete obj[key];
});
};
db.getCollection('Collection').find({}).forEach((data) => {
remove(data);
db.getCollection('OtherCollection').insert(data);
})