在MongoDB中，获取集合中的记录数可以使用countDocuments()方法。该方法返回一个promise，可以使用then()方法来获取结果。
以下是一个示例：
const MongoClient = require('mongodb').MongoClient;
const uri = "mongodb+srv://<username>:<password>@<cluster-url>/<database>?retryWrites=true&w=majority";
MongoClient.connect(uri, function(err, client) {
if(err) {
console.log('Error occurred while connecting to MongoDB Atlas...\n',err);
}
console.log('Connected to MongoDB Atlas...');
const collection = client.db("<database>").collection("<collection>");
collection.countDocuments()
.then(count => {
console.log("Number of documents in the collection: ", count);
})
.catch(err => {
console.log("Error occurred while counting documents:\n", err);
})
.finally(() => {
client.close();
});
});
请注意，<username>、<password>、<cluster-url>、<database>和<collection>都需要替换为适当的值。
