connection.js

const Sequelize = require("sequelize");
module.exports = new Sequelize({
  database: "test",
  username: "root",
  password: "mysecretpassword",
  dialect: "postgres",
});

index.js

const { DataTypes, Model } = require("sequelize");
const sequelize = require("./connection");

(async () => {
  const Ship = sequelize.define("ship", {
    name: {
      type: DataTypes.STRING,
      allowNull: false,
    },
    purpose: {
      type: DataTypes.STRING,
      allowNull: false,
    },
  });
  const Member = sequelize.define("member", {
    name: {
      type: DataTypes.STRING,
      allowNull: false,
    },
    species: {
      type: DataTypes.STRING,
      allowNull: false,
    },
  });

  Member.belongsTo(Ship);
  Ship.hasMany(Member);

  await sequelize.sync({ force: true });

  const enterprise_ship = await Ship.create({
    name: "Enterprise",
    purpose: "exploration",
  });
  const m1 = await Member.create({ name: "Kirk", species: "human" });
  const m2 = await Member.create({ name: "Spock", species: "hybrid" });

  await m1.setShip(enterprise_ship);
  await m2.setShip(enterprise_ship);

  console.log(m1.toJSON());
  console.log(m2.toJSON());
  console.log(await m2.getShip());
})();