Let's now write our first Sequelize program. For this, you have to install sequelize, pg pg-hstore packages. We will continue using the same project from previous level. Run the following command in the terminal:
npm install sequelize pg pg-hstore
Once the packages are installed, create a new file connectDB.js:
// connectDB.js
const Sequelize = require("sequelize");
const database = "todo_db";
const username = "postgres";
const password = "changeme";
const sequelize = new Sequelize(database, username, password, {
host: "localhost",
dialect: "postgres",
});
sequelize
.authenticate()
.then(() => {
console.log("Connection has been established successfully.");
})
.catch((error) => {
console.error("Unable to connect to the database:", error);
});This file, connectDB.js, will connect our program with the Postgres database server running on our computer. Postgres is a multi-user database server - this means its process runs in the background of our computer, and any program that wants to talk to it has to first connect to it. This is what we're doing with the sequelize.authenticate(). Note that we've used the database name as todo_db, and password as changeme - both of these were set in the previous target.
Once a connection is established with the server, we can then issue commands to it using Sequelize. First, you have to modify connectDB.js to export two functions. In Node.js, we export functions, objects etc. in a module to outside world to consume using module.exports.
const Sequelize = require("sequelize");
const database = "todo_db";
const username = "postgres";
const password = "changeme";
const sequelize = new Sequelize(database, username, password, {
host: "localhost",
dialect: "postgres",
});
const connect = async () => {
return sequelize.authenticate();
}
module.exports = {
connect,
sequelize
}Alright, now we have set up Postgres on our computer and used Sequelize to connect to the database! Next, we'll learn how to create, update and query the table using Sequelize.