How sequelize works?

Question

I\'m trying to understand how sequelize works on a simple example : User can have many posts and post can have only one user.

First question, I don\'t know if I have to

Answer 1

I am really just restrucuring your code.

// Create One database config file

var Sequelize=require('sequelize');

var connection=new Sequelize('project','user','password',{
    dialect:'mysql',
    logging:false
});

connection.authenticate()
  .then(() => {    
    console.log("Connected to database");
  })
  .catch(err => {
    //console.error("Can't connect to database :(\n", err);
  });


module.exports={
    database:connection,
}

//Your User Schema File

var database = require('your_file_path/DatabaseConnection').database;

var Sequelize = require('sequelize');

var Users = database.define('users', {

    username: {
        allowNull: false,
        type: Sequelize.STRING,
        unique: true
    },
    password: {
        allowNull: false,
        type: Sequelize.STRING
    },
    email: {
        allowNull: false,
        type: Sequelize.STRING,
        unique: true
    }
}, {
    underscored: true
},hooks: {
    beforeCreate: (user, option) => {
        users.password = encrypto.encryptEntity(user.password);
        //for automatic encryption of password
    },

}

);

  Users.sync();

    //id, updated_at , and modified_at will be maintained by default

    module.exports = {
        Users
    }

// your post file path

var Posts = database.define('posts', {

    post_content: {
        allowNull: false,
        type: Sequelize.STRING,
        unique: true
    }
}, {
    underscored: true
});

//importing User
var Users = require('file_path')

Users.hasMany(Posts, {
    foreignKey: 'user_id',
    sourceKey: 'user_id',
    onDelete: 'cascade',
    as:'Posts',
});

Posts.belongsTo(Users, {
    foreignKey: 'user_id',
    sourceKey: 'user_id',
    onDelete: 'cascade',
    as:'Users',
}); 
// two way binding.
Posts.sync();

BY maintaining Relation you can easily update data using setter and getter methods

Posts.setUsers(user_object);

// above code will automatically put the user_id found in user_object

//for select query you can use:

Users.findOne({
    where:{
        id:user_id
    },
    include: [{
        model: Posts,
        attributes: ['post_content'],
        as: "Posts"
    }//this will bring every posts user has created
})

I think above coding standard will make your code looks cleaner and will be more helpful for larger projects.

Hope this helps.