如何使用 Mongoose 从 NodeJS 中的 MongoDB Change Streams 获取 fullDocumentBeforeChange？

Question

I'm using Mongoose and MongoDB and Nodejs and I want to listen for changes to a MongoDB collection and console log the document before change and the update description.

The actual result: I can only log the update description.

const didChangeStream = model.collection.watch({
  fullDocument: 'updateLookup',
  fullDocumentBeforeChange: 'whenAvailable'
});
didChangeStreamAlert.on('change', async (event) => {
  const {
    documentKey,
    fullDocument,
    fullDocumentBeforeChange,
    updateDescription
  } = event;
  console.log('fullDocumentBeforeChange', fullDocumentBeforeChange);
  console.log('updateDescription', updateDescription);
});

Answer 1

https://mongoosejs.com/docs/api.html#model_Model-watch says the options is a second argument, so must be

const didChangeStream = model.watch([], {
  fullDocument: 'updateLookup',
  fullDocumentBeforeChange: 'whenAvailable'
});

And it should work on model level. No need to touch model.collection directly.