// You can do it with a string.
const Sequelize = require('sequelize');
const sequelize = new Sequelize("mssql://username:password@mydatabase.database.windows.net:1433", 
 { pool: {
    "max": 10,
    "min": 0,
    "idle": 25000,
    "acquire": 25000,
    "requestTimeout": 300000
  },
  dialectOptions: {
    options: { encrypt: true }
  }
  });
      // This uses the Raw Query to query for all dbs for example
  sequelize.query(`  
                SELECT name, database_id, create_date  
                FROM sys.databases   
                GO `, 
  { type: sequelize.QueryTypes.SELECT})
    .then(async dbs => {
      console.log("dbs", dbs);
      return dbs;
    });```


Example above: mssql db hosted on Azure. 

Example below: mssql db on localhost. 

You can do it with key value pairs or a string.

`
var Sequelize = require("sequelize");

var sequelize = new Sequelize("sequelize_db_name", user, password, {
  host: "localhost",
  port: 1433,
  dialect: "mssql",
  pool: {
    max: 5,
    min: 0,
    idle: 10000
  },
  dialectOptions: {
    options: { encrypt: true }
  }
});`

Based on this article you should install sequelize-msnodesqlv8:

var sequelize = new Sequelize({
  dialect: 'mssql',
  dialectModulePath: 'sequelize-msnodesqlv8',
  dialectOptions: {
    instanceName: 'MSSQLSERVER01',
    trustedConnection: true
  },
  host: 'localhost',
  database: 'master'
});

or perhaps better:

var sequelize = new Sequelize({
  dialect: 'mssql',
  dialectModulePath: 'sequelize-msnodesqlv8',
  dialectOptions: {
    connectionString: 'Server=localhost\MSSQLSERVER01;Database=master; Trusted_Connection=yes;'
  },
});

But you should not leave default database as Master. Use your database name instead.

Mark this:

There are many node mssql clients and sequelize defaults to using tedious, but being pure javascript,tedious lacks support for integrated security. msnodesqlv8 is a client that interfaces with a native odbc library. This allows integrated security to be used. It does require additional binaries to deploy, but fortunately, msnodesqlv8 is distributed with binaries for the most common architectures

You are using integrated security, so you need to deal with that problem.

See also this question.