Node の MongoDB Driver

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Prior to 《Node の MongoDB install 》 Among article , It mainly talks about how to install MongoDB And its visual interface Compass.

Now let's talk about node How to connect and use MongoDB, about node Connect , There are two ways , All download Libraries ：

• mongodb： MongoDB There is a basic library mongodb(Node.js MongoDB Driver)
• Mongoose: Now the mainstream Library , Better in the amount of code , Just add, delete, modify and check the recommendation

mongodb

This is the basic library , But there are basic functions , If the demand is not too much, use this .

download

Installation command ：yarn add mongodb

May refer to ：https://www.mongodb.org.cn/drivers/5.html

Then create mongo The folder and index.js, It says in it mongodb How to use the library .

nodemon The main program running is main.js

Connect

First test mongodb Does the database exist , Whether it can be connected .

from mongodb Import... In the library MongoClient Client module , This module can be used to connect to the database

The test method is as follows ：( there baseUrl It is based on the address of the previous database , You can also view the database to be connected in the visual interface url)

const MongoClient = require('mongodb').MongoClient;const baseUrl = 'mongodb://127.0.0.1:27017/mongodbTest'function TestConnect() {    MongoClient.connect(baseUrl, function(err, db) {        if (err) throw err;        console.log(" Database created !");        db.close();    });}

function ：

But in fact, at this time, the database mongodbTest Not created , In the visual interface compass perhaps cmd None of them

then , I searched online for half a day , I found that this is only connected to 27017 Where? , No nonexistent database is created .（ The code in this rookie tutorial should be wrong ）

So let's create a database manually , You can create , A little bit more simple , Then you can create another set in the database .

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Wait a minute , Next I'll go mongodb There was a wave of search on the official website , Finally, I successfully created the database with code , And the method on the rookie really doesn't work .

PS: There is a boiling point here , And dig you gave a relatively complete reply , Ha ha ha

The previous test connection method can be slightly modified , Use async and await To carry out , This makes the code look more comfortable .

mongodb official API：https://mongodb.github.io/node-mongodb-native/4.5/

It's used here MongoClient.db Method , This method will use or establish a database , however , If you don't create a collection for this database , Then this database will not be generated .

const baseUrl = 'mongodb://127.0.0.1:27017'//  Create objects const client = new MongoClient(baseUrl);async function TestConnect() {    try {        //  Connect to database         await client.connect();        //  Use the previously manually created mongodbTest database         const db = await client.db('mongodbTest');        console.log(db.databaseName)        //  Create a new collection  ( If the database is created by the code , Then you must create a set )        db.createCollection('collection01')    } catch(e) {        console.log(e)        await client.close();    }}module.exports = { TestConnect }

Get collection list

Now that you have successfully created the database , Then try to get all the collection information under the database collections, have access to collectionName Print out the names of these sets

//  Connect to database await client.connect();//  Use the previously manually created mongodbTest database const db = await client.db('mongodbTest');//  Get all collections under the current database let collections = await db.collections();//  Print set name collections.forEach(item=>{    console.log(item.collectionName)})

Set list name ：

After the above simple use of the database and set list , You can operate on a single set .

PS: For the database db Please refer to specific API file , The methods inside are also relatively comprehensive

Create a collection and insert data

Use here db Medium createCollection Method , Can be used to create new collections

createCollection Method parameter ：

Parameters	effect
name	Create the name of the collection
Optional	Command optional settings
callback	The callback method ,Callback<Collection<TSchema>>

Test code ：

//  Create a new collection db.createCollection('collection03', { autoIndexId: true }, (err, res)=>{    if (err) console.log(' Collection creation failed ');    console.log(res.collectionName)  // collection03})

After creating an empty collection , It's time to insert data into this set

stay mongodb in , Most of the collections are documents , Or the front end can be regarded as a key value pair JSON data

example ： Define a document , And use insertOne Insert into the target set ：

//  Use set collection03let c3 = db.collection('collection03');//  Define documents let doc = {    name: ' Zhang San ',    age: 18,    hobby: ' Hit Li Si ',}//  Insert the document into the collection const result = await c3.insertOne(doc);

insertOne If the insertion is successful , Will return the current document in the collection id

There are the following methods for inserting documents into collections 3 Kind of ：（ The return values of these three methods are Promise, have access to async and await To solve the callback ）

• insert： Insert a single document or an array of documents MongoDB. If the incoming document does not contain \u id Field , The driver will add a , Thus changing the document
• insertMany： Insert the document array MongoDB. If the incoming document does not contain \u id Field , The driver will add a , Thus changing the document
• insertOne： Insert a single document MongoDB. If the incoming document does not contain \u id Field , The driver will add a , Thus changing the document

Next try inserting a document array ：

let doc = [    {        name: ' Li Si ',        age: 18,        hobby: ' Beat Wang Wu ',    },    {        name: ' Wang Wu ',        age: 18,        hobby: ' Open three ',    },]//  Insert the document into the collection const result = await c3.insertMany(doc);

Read the data in the collection

The document content has been inserted into the database collection above , So how to read the data from the database ？

MongoDB The library provides find Method

Method	effect
find	Create a cursor for the filter , This filter can be used for iterations MongoDB Result
findOne	Get the first document that matches the filter
findOneAndDelete	Find the document and delete it in an atomic operation , Need to write lock during operation
findOneAndReplace	Find the document and replace it in an atomic operation . Need to write lock during operation
findOneAndUpdate	Find the document and update it in an atomic operation . Need to write lock during operation

Example : You need to use toArray Change my , Or you can use the callback method to view

//  Read the data in the collection const res = await c3.find().toArray();console.log(res)

If when retrieving data , You need to filter out some useless data , So it can be find Write parameters to configure .

Use here projection Limit the fields returned , Set the property that does not need to be read to 0, Or set the content to be read as 1.

Be careful , It is better not to set 0 and 1, Just set the read perhaps Do not read . Otherwise, there may be an error ：MongoServerError: Cannot do inclusion on field name in exclusion projection （ If you specify 0 and 1 value , There will be errors , Unless one of the fields is \u id Field ）

The following example is to _id and age Do not read ：

//  Read the data in the collection const res = await c3.find({}, {     projection: { _id: 0, age: 0 }}).toArray();console.log(res)

result ：

In the example above , Will find find The first parameter in the method is {}, Because this is the query object , Used to restrict search . You can use to filter .

query Example ：

//  Read the data in the collection const res = await c3.find({    name: / Zhang /}, {     projection: { _id: 0, age: 0 }}).toArray();console.log(res)

In this way, only Zhang San's information is returned ：

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Delete set information

Now try to delete the previously saved documents from the collection

There are also delete Delete method

Method	effect
deleteOne	Delete a single document from the collection
deleteMany	Delete the document array from the collection

//  Read the data in the collection const res = await c3.deleteOne({    name: / Zhang /});console.log(res)  // { acknowledged: true, deletedCount: 1 }

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Update collection

The above has been written with additions and deletions , Now? curd There are updates left

Method	effect
update	It is not recommended to use , It is recommended to use the following two
updateOne	Update a single document in the collection
updateMany	Update multiple documents in the collection

Example ：

//  Read the data in the collection let newvalue = { $set: { hobby: ' Hit Li Si ' } }const res = await c3.updateOne({    name: / king /}, newvalue);console.log(res)

here , Wang Wu's hobby in the database has changed from playing Zhang San to playing Li Si

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That's all mongodb Basic use of Library , I didn't expect to write so much .

mongoose Save it for next time …