How do I get SvelteKit and TypeORM to work together?

TypeORM is a popular TypeScript ORM (Object-Relational Mapper) that works with various databases, while SvelteKit is a framework built on Svelte for developing efficient Server-Side Rendering (SSR) and Static Site Generation (SSG) applications. Combining these technologies provides robust data persistence and manipulation capabilities for Svelte applications.

In a SvelteKit application, integrating TypeORM primarily involves the following steps:

1. Install Dependencies

First, install TypeORM and the database driver in your SvelteKit project. For example, if using PostgreSQL, install the following packages:

bash
npm install typeorm pg

2. Configure TypeORM

Next, create a TypeORM configuration file. Typically named ormconfig.json and located in the project root, it contains detailed database connection information, as shown below:

json
{
  "type": "postgres",
  "host": "localhost",
  "port": 5432,
  "username": "your_username",
  "password": "your_password",
  "database": "your_database",
  "synchronize": true,
  "logging": false,
  "entities": [
    "src/entity/**/*.ts"
  ],
  "migrations": [
    "src/migration/**/*.ts"
  ],
  "subscribers": [
    "src/subscriber/**/*.ts"
  ]
}

3. Initialize Database Connection

In a SvelteKit application, initialize the database connection on the server side. Perform this within the handle hook in src/hooks.ts, as illustrated:

typescript
import { createConnection } from 'typeorm';
import type { Handle } from '@sveltejs/kit';

export const handle: Handle = async ({ request, resolve }) => {
  const connection = await createConnection();

  // Use the TypeORM connection object here
  // ...

  const response = await resolve(request);

  // Close the connection after response is sent
  connection.close();

  return response;
};

4. Define Entities

Define TypeORM entities in your SvelteKit application. Entities are classes corresponding to database tables. For example:

typescript
import { Entity, PrimaryGeneratedColumn, Column } from 'typeorm';

@Entity()
export class User {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  // Other properties and columns...
}

5. Use Entities for Database Operations

In SvelteKit endpoints (typically .ts files in src/routes), use defined entities to perform CRUD operations. For example:

typescript
import type { RequestHandler } from '@sveltejs/kit';
import { getRepository } from 'typeorm';
import { User } from '../entity/User';

export const get: RequestHandler = async () => {
  const userRepository = getRepository(User);
  const users = await userRepository.find();

  return {
    status: 200,
    body: users,
  };
};

export const post: RequestHandler<{}, FormData> = async (request) => {
  const userRepository = getRepository(User);
  const newUser = userRepository.create(request.body);
  await userRepository.save(newUser);

  return {
    status: 303,
    headers: {
      location: '/users'
    }
  };
};

These steps outline the basic integration process for TypeORM in a SvelteKit application. In actual development, you may need additional configurations such as setting up connection pools, handling transactions, using middleware for connection management, and addressing security and performance optimization concerns.