postgres init code with multiple sequelize

Question

I am trying to convert js code to ts code (and understanding why something have been done).

This my JS code

use strict';

const fs = require('fs');
const path = require('path');
const Sequelize = require('sequelize');
const basename = path.basename(__filename);
const env = process.env.NODE_ENV || 'development';
const config = require(__dirname + '/../config/config.js')[env];
const db = {};

let sequelize;
if (config.use_env_variable) {
  sequelize = new Sequelize(process.env[config.use_env_variable], config);
} else {
  sequelize = new Sequelize(config.database, config.username, config.password, config);
}


Object.keys(db).forEach(modelName => {
  if (db[modelName].associate) {
    db[modelName].associate(db);
  }
});

db.sequelize = sequelize;
db.Sequelize = Sequelize;

module.exports = db;

Here, there are multiple sequalise

db.sequelize = sequelize;
db.Sequelize = Sequelize;

Can someone please help me in understand meaning, purpose and why both of them exist? and where we would use each of them.

I am able to make sense for sequelize but not for Sequelize. like we already have used new Sequelize( so why would we add it in db object?

How can we know why who wrote the code added that property, without exploring the codebase and detecting where db.Sequelize was used? It may be useless and never used, or it may be necessary in some other sections of the software. We have no way to know that — gbalduzzi
– gbalduzzi, Commented Jul 30, 2021 at 15:38

niour · Accepted Answer · 2021-07-31 01:13:48Z

1

+100

Sequelize refers to the library itself while sequelize refers to an instance of Sequelize, which represents a connection to one database. This is the recommended convention and it is followed throughout the official documentation of sequelize also.

So for example a db.Sequelize.fn() is utilizing a specific function from sequelize module and db.sequelize.model.findAll() is utilizing an instance from a connection to a specific database.

answered Jul 31, 2021 at 1:13

niour

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