What is callback in Mongoose?

What is callback in Mongoose?

Anywhere a callback is passed to a query in Mongoose, the callback follows the pattern callback(error, results) . What results is depends on the operation: For findOne() it is a potentially-null single document, find() a list of documents, count() the number of documents, update() the number of documents affected, etc.

Is findByIdAndUpdate deprecated?

findByIdAndUpdate() is issuing a deprecation warning for mongodb – which has deprecated collection. findAndModify. Mongodb suggests using findOneAndUpdate, findOneAndReplace or findOneAndDelete instead. ensureIndex is also deprecated – mongodb suggests using createIndexes instead.

How do I use findOne update?

As the name implies, findOneAndUpdate() finds the first document that matches a given filter , applies an update , and returns the document. By default, findOneAndUpdate() returns the document as it was before update was applied. You should set the new option to true to return the document after update was applied.

What does findOneAndUpdate return?

Return Value The collection. findOneAndUpdate() action returns a Promise that resolves to a single document that the query overwrote. If no documents match the specified query, the promise resolves to null .

What is deprecation warning in mongoose?

By default, mongoose. connect() will print out the below warning: DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.

What is Upsert in mongoose?

In MongoDB, an upsert means an update that inserts a new document if no document matches the filter . To upsert a document in Mongoose, you should set the upsert option to the Model. updateOne() function: const res = await Character. Mongoose will insert at most one document.

How is the find byidandupdate function used in mongoose?

Mongoose | findByIdAndUpdate () Function. The findByIdAndUpdate () function is used to find a matching document, updates it according to the update arg, passing any options, and returns the found document (if any) to the callback.

What does findoneandupdate do in MongoDB?

With the exception of an unindexed upsert, findOneAndUpdate () is atomic. That means you can assume the document doesn’t change between when MongoDB finds the document and when it updates the document, unless you’re doing an upsert.

What is the function to find a document in mongoose?

Mongoose | findOneAndUpdate () Function. The findOneAndUpdate () function is used to find a matching document and update it according to the update arg, passing any options, and returns the found document (if any) to the callback.

When to use upsert or findone and update in mongoose?

An upsert behaves like a normal findOneAndUpdate () if it finds a document that matches filter. But, if no document matches filter, MongoDB will insert one by combining filter and update as shown below. Mongoose transforms the result of findOneAndUpdate () by default: it returns the updated document.

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