How to use TypeScript with Sequelize

Using Decorators is something you should avoid as much as possible, they are not ECMAScript standard. They are even consider legacy. It is why I'm going to show you how to use sequelize with typescript.

we just need to follow the docs: https://sequelize.org/v5/manual/typescript.html but as it is not very clear, or at least to me. It took me a while understand it.

There it says that you need to install this tree things

 * @types/node * @types/validator // this one is not need it * @types/bluebird

npm i -D @types/node @types/bluebird

then let's assume your project looks like so:

myProject--src----models------index.ts------user-model.ts------other-model.ts----controllers----index.ts--package.json

Let's create the user model first

`./src/models/user-model.ts`import { BuildOptions, DataTypes, Model, Sequelize } from "sequelize";export interface UserAttributes {    id: number;    name: string;    email: string;    createdAt?: Date;    updatedAt?: Date;}export interface UserModel extends Model<UserAttributes>, UserAttributes {}export class User extends Model<UserModel, UserAttributes> {}export type UserStatic = typeof Model & {    new (values?: object, options?: BuildOptions): UserModel;};export function UserFactory (sequelize: Sequelize): UserStatic {    return <UserStatic>sequelize.define("users", {        id: {            type: DataTypes.INTEGER,            autoIncrement: true,            primaryKey: true,        },        email: {            type: DataTypes.STRING,            allowNull: false,            unique: true,        },        name: {            type: DataTypes.STRING,            allowNull: false,        },        createdAt: {            type: DataTypes.DATE,            allowNull: false,            defaultValue: DataTypes.NOW,        },        updatedAt: {            type: DataTypes.DATE,            allowNull: false,            defaultValue: DataTypes.NOW,        },    });}

Now just to play arrow let's create another-model.ts

`./src/models/another-model.ts`import { BuildOptions, DataTypes, Model, Sequelize } from "sequelize";export interface SkillsAttributes {    id: number;    skill: string;    createdAt?: Date;    updatedAt?: Date;}export interface SkillsModel extends Model<SkillsAttributes>, SkillsAttributes {}export class Skills extends Model<SkillsModel, SkillsAttributes> {}export type SkillsStatic = typeof Model & {    new (values?: object, options?: BuildOptions): SkillsModel;};export function SkillsFactory (sequelize: Sequelize): SkillsStatic {    return <SkillsStatic>sequelize.define("skills", {        id: {            type: DataTypes.INTEGER,            autoIncrement: true,            primaryKey: true,        },        skill: {            type: DataTypes.STRING,            allowNull: false,            unique: true,        },        createdAt: {            type: DataTypes.DATE,            allowNull: false,            defaultValue: DataTypes.NOW,        },        updatedAt: {            type: DataTypes.DATE,            allowNull: false,            defaultValue: DataTypes.NOW,        },    });}

Our Entities are done. now the db connection.

open ./src/models/index.ts there is where we gonna place the seqelize instance

`./src/models/index.ts`import * as sequelize from "sequelize";import {userFactory} from "./user-model";import {skillsFactory} from "./other-model";export const dbConfig = new sequelize.Sequelize(    (process.env.DB_NAME = "db-name"),    (process.env.DB_USER = "db-user"),    (process.env.DB_PASSWORD = "db-password"),    {        port: Number(process.env.DB_PORT) || 54320,        host: process.env.DB_HOST || "localhost",        dialect: "postgres",        pool: {            min: 0,            max: 5,            acquire: 30000,            idle: 10000,        },    });// SOMETHING VERY IMPORTANT them Factory functions expect a// sequelize instance as parameter give them `dbConfig`export const User = userFactory(dbConfig);export const Skills = skillsFactory(dbConfig);// Users have skills then lets create that relationshipUser.hasMay(Skills);// or instead of that, maybe many users have many skillsSkills.belongsToMany(Users, { through: "users_have_skills" });// the skill is the limit!

on our index.ts add, if you just want to open connection

  db.sequelize        .authenticate()        .then(() => logger.info("connected to db"))        .catch(() => {            throw "error";        });

or if you want to create them tables

  db.sequelize        .sync()        .then(() => logger.info("connected to db"))        .catch(() => {            throw "error";        });

some like this

 import * as bodyParser from "body-parser";import * as express from "express";import { dbConfig } from "./models";import { routes } from "./routes";import { logger } from "./utils/logger";import { timeMiddleware } from "./utils/middlewares";export function expressApp () {    dbConfig        .authenticate()        .then(() => logger.info("connected to db"))        .catch(() => {            throw "error";        });    const app: Application = express();    if (process.env.NODE_ENV === "production") {        app.use(require("helmet")());        app.use(require("compression")());    } else {        app.use(require("cors")());    }    app.use(bodyParser.json());    app.use(bodyParser.urlencoded({ extended: true, limit: "5m" }));    app.use(timeMiddleware);    app.use("/", routes(db));    return app;}

Once again the sky is the limit.If you do this you'll have all the power of the autocomplete.here an example: https://github.com/EnetoJara/resume-app

Use sequelize-typescript. Convert your tables and views into a class that extends Model object.

Use annotations in classes for defining your table.

import {Table, Column, Model, HasMany} from 'sequelize-typescript'; @Tableclass Person extends Model<Person> {   @Column  name: string;   @Column  birthday: Date;   @HasMany(() => Hobby)  hobbies: Hobby[];}