mongoose general usage methods #mongoose #mongodb #database #mongo

mongo.js

// Playground: https://mongoplayground.net/
// Documentation: https://mongoosejs.com/docs/
// Cheatsheet1: https://kb.objectrocket.com/mongo-db/the-mongoose-cheat-sheet-225
// Cheatsheet2: https://github.com/azat-co/cheatsheets/blob/master/mongodb-mongoose/readme.md

const {Schema, model, connect} = require("mongoose");

let log = console.log;

function connectMongoDb() {
  log("Connecting to database☻...");
  connect("mongodb://localhost/admin", {
    useNewUrlParser: true,
    useUnifiedTopology: true,
    useFindAndModify: false,
    useCreateIndex: true,
  });
  // .then(() => {
  //   log("connection successful☺");
  // })
  // .catch((error) => {
  //   log("error connection to MongoDB:", error.message);
  // });
}

const noteSchema = new Schema({
  name: {
    type: String,
    required: true,
    unique: true,
    minlength: 4,
  },
  born: {
    type: Number,
  },
});

const userSchema = new Schema({
  username: {
    type: String,
    required: false,
    unique: false,
    minlength: 2,
  },
  name: {
    type: String,
  },
  friends: { [{type: Schema.Types.ObjectId, ref: GADGET_COLLECTION_NAME}] } // This tells joining to another collection name.
});

const userModel = model("User", userSchema);
const noteModel = model("Note", noteSchema); // ? Not used in below code though.

connectMongoDb();

async function main() {
  log("$log1-", await userModel.collection.countDocuments());
  log("$log2-", await userModel.find({})); // This returns an array of document(objects).Yikes!!!

  log("$log3-", await userModel.find({phone: {number: 235234}}));
  log("$log4-", await userModel.findOne({name: "sahil"}));
  log("$log5-", await userModel.findById("asfasf92h9sh9sf").populate("friends"));// You are supposed to pass the fieldName while calling populate method instead of the name of collection.(name of collectionn is required in the schema definition i.e., `userSchema`)
  log("$log5-", await userModel.findById("asfasf92h9sh9sf").populate("friends"));

  userModel.findByIdAndUpdate(id, updatedObject, {new: true}); //Though it is EQUIVALENT TO findOneAndUpdate(_id: id, ...)
  // By default, findByIdAndUpdate() returns the document as it was **before** update was applied. If you set new: true, findOneAndUpdate() will instead give you the object after update was applied. To change the default to true, use mongoose.set('returnOriginal', false);.
  userModel.findByIdAndRemove(id, options); // return Query
  // ? // userModel.findByIdAndRemove(id, ...) IS EQUIVALENT TO findOneAndRemove({ _id: id }, ...)

  await userModel.deleteMany({});
  // ? Detele all documents in ^^ the collection modelUser.

  await userModel.collection.insertOne((desiredObjet = {}));
  await userModel.collection.insertMany((desiredObjet = {})); //To write many documents.
  await userModel.collection.bulkWrite((desiredObject = {})); //To write many documents.

  try {
    const userSaved = await new userModel({username: "superman9"}).save(); //This line just create the _id property for the object, and checks for any error acc. to schema.
    log("saveduser- ", userSaved);
  } catch (error) {
    log(`#me error: ${error.message} ==produced by== ${error.name}`);
    // ? Handle from here for failed attempt only according to the error that is produced,
    // ? you can send this eroor to frontend to, and do appropriate actions here only.
  }
}

main();

// =========================
function usingPromiseCallback() {
  new userModel({username: "barfillamaan22"}) //(1)This line just create the _id property for the object.
    .save() // (1)This method first checks the authenticity against the defined criteria in schema and (2)then tries to save accordingly, and (3)returns the object with additional __v property.
    .then((q) => log("Yikess..!!", q)) //(1)This method executes on succesful saving to database operation.
    .catch((err) => log(`==NAKED ERROR== "${err.message} ==produced by== ${err.name}"`));
}

// =========================
//src: Ademola's abstract code for doing save and populate, sinle liner.
// const savedBlog = await (await blog.save())
//   .populate("user", {
//     username: 1,
//     name: 1,
//     _id: 1,
//   })
//   .execPopulate();