js-mongoose-tutor.md

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• Mongoose Crash Course - Beginner Through Advanced
  • Install
  • Schema
  • MongoDB Operation Example
  • Schema Validataion
  • SQL join ?
  • Schema Methods

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Mongoose Crash Course - Beginner Through Advanced

mongodb cheat sheet

Install

$ npm init -y
$ npm install mongoose

Schema

// User.js
const mongoose = require('mongoose');

const Schema = mongoose.Schema;

const userSchema = new Schema({
    name: String,
    email: String
});

// `User` collection
const User = mongoose.model('User', userSchema);

module.exports = User;

• more field schema example

  const userSchema = new Schema({
      name: String,
      age: Number,
      email: String,
      createAt: Date,
      updateAt: Date,
      bestFriend: mongoose.Schema.Types.ObjectId,
      hobbies: [String],
      address: {
          street: String,
          city: String
      },
      // use another schema
      address2: addressSchema
  });

MongoDB Operation Example

const mongoose = require('mongoose');
const User = require('./user');

mongoose.connect('mongodb://localhost:27017/test' )


async function run() {
    // create new user
    const user = new User({
        name: 'John',
        email: '[email protected]'
    });
    await user.save();  // sync to database

    // create another user on database
    const user2 = await User.create ({
        name: 'Bob',
        email: '[email protected]'
    });

    const users = await User.find();
    console.log(users);
}

run()

Schema Validataion

const userSchema = new Schema({
    name: String,
    age: {
        type: Number,
        min: 1,
        max: 100,
        validate: { // customize validator
            validator: v => v % 2,
            message: props => `${props.value} is not an even number`
        }
    }
    email: {
        type: String,
        minLength: 10,
        required: true, // must provide email when creating new user
        lowercase: true, // automatically convert string to lowercase
    },
    createAt: {
        type: Date,
        immutable: true,  // never let us change it 
        default: () => Date.now(), // default value
    },
    bestFriend: {
        type: mongoose.Schema.Types.ObjectId,
        ref: "User"  // tells mongoose what model does this object id reference
    },
});

• schema validation in mongoose only works on create() or save().
  • but there's a bunch of other methods built into mongoose that you can use to update things in your database without using the create() or save() method, and those don't go through validation because they work directly on the mongodb database.
• don't use those method, such like findByIDAndUpdate, updateOne, updateMany, those do not go through validataion.
• which I always recommend you always doing just a normal findByID or findOne() get your user and then save() it.

SQL join ?

user = User.where("age")
    .gt(12)
    .where("name")
    .equals("Kyle")
    .limit(1)

• you're query user, how to get the information of bestFriend as well ?

  user = User.where("age")
      .gt(12)
      .where("name")
      .equals("Kyle")
      .populate("bestFriend")
      .limit(1)

  ...
  age:26,
  bestFriend: {
      _id: .... ,
      name: ... ,
      age: ... ,
      ...
  }

Schema Methods

// instance method
userSchema.methods.sayHello = function() {
    console.log('Hello, my name is ' + this.name);
}

// static method
userSchema.statics.findByName = function(name) {
    return this.find({ name: new RegExp(name, 'i') });
}

// query method
userSchema.query.byName = function(name) {
    // this is going to be chainable with a query
    return this.where({ name: new RegExp(name, 'i') });
}

// virtual property
userSchema.virtual('fullName').get(function() {
    return this.name.first + ' ' + this.name.last;
});
// use: user.fullName

// middle ware
userSchema.pre('save', function(next) {
    this.updateAt = new Date();
    next();
});

userSchema.post('save', function(doc,next) {
    doc.sayHello()
    next();
});