I can see output from console.log('hello world') in the Output tab, but not with console.log(db.collectionName.find({}).length)
console.log('hello world')
console.log(db.collectionName.find({}).length)
UPDATE: I found a fix: console.log(db.collectionName.find({}).toArray().length)
console.log(db.collectionName.find({}).toArray().length)