How nodejs operates mongodb to add, delete, modify and check

With the gradual development of front-end technology, Node.js has gradually become one of the necessary skills for front-end developers. Operating the MongoDB database in Node.js is also an inevitable part of daily development. So, how to perform addition, deletion, modification and query operations in MongoDB in Node.js?

1. Install the MongoDB driver

Before operating MongoDB in Node.js, we need to install the MongoDB driver first. It can be installed directly via npm.

npm install mongodb --save

2. Connect to the database

Before using MongoDB, we need to establish a connection with the database first.

const MongoClient = require('mongodb').MongoClient;

// 数据库地址
const dbUrl = 'mongodb://localhost:27017/';

// 指定数据库名称
const dbName = 'test';

// 建立连接
MongoClient.connect(dbUrl, function(err, client) {
  if (err) {
    console.log(err);
    return;
  }

  console.log('连接数据库成功');

  // 获取数据库
  const db = client.db(dbName);

  // 关闭连接
  client.close();
});

3. Insert data

In MongoDB, we use collection to represent a collection. You can obtain a collection through the db.collection method.

const collectionName = 'users';
const insertData = { name: 'Tom', age: 18 };
db.collection(collectionName).insertOne(insertData, function(err, res) {
  if (err) {
    console.log(err);
    return;
  }

  console.log('插入数据成功');

  client.close();
})

4. Querying data

Querying data is one of the most commonly used operations in MongoDB. We can query the data in the database through the collection.find method. The find method returns a reference to the Cursor object. We need to traverse the Cursor object to obtain all query results.

const collectionName = 'users';
const findQuery1 = { name: 'Tom' };
const findQuery2 = { age: { $lt: 30 } };
const fields = { _id: 0, name: 1, age: 1 };
db.collection(collectionName).find(findQuery1, fields).toArray(function(err, docs) {
  if (err) {
    console.log(err);
    return;
  }

  console.log(docs);

  client.close();
});

5. Update data

In MongoDB, we can use the collection.updateOne method to update a piece of data in the collection. Update conditions and update content need to be specified.

const collectionName = 'users';
const filter = { name: 'Tom' };
const updateData = { $set: { age: 20 } };
db.collection(collectionName).updateOne(filter, updateData, function(err, res) {
  if (err) {
    console.log(err);
    return;
  }

  console.log('更新数据成功');

  client.close();
});

6. Deleting data

In MongoDB, we use the collection.deleteOne method to delete an item of data in the collection. Deletion conditions need to be specified.

const collectionName = 'users';
const filter = { name: 'Tom' };
db.collection(collectionName).deleteOne(filter, function(err, res) {
  if (err) {
    console.log(err);
    return;
  }

  console.log('删除数据成功');

  client.close();
});

7. Summary

The above is the basic content of the addition, deletion, modification and query operations of the MongoDB database in Node.js. In actual development, we need to reasonably use the above methods according to different business needs to operate the database more efficiently.

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