Node MySQL initialization snippet

db.ts

import mysql, { Connection } from "mysql";
import { DB_HOST, DB_PASSWORD } from "./env";

const databaseName = "xxx";
const databaseUser = "xxx";
const databasePort = 1234;

export const getConn: () => Connection = (() => {
  let conn: Connection;
  process.on("exit", () => {
    if (conn) conn.destroy();
  });
  return () => {
    if (conn) return conn;
    conn = mysql.createConnection({
      host: DB_HOST,
      database: databaseName,
      user: databaseUser,
      port: databasePort,
      password: DB_PASSWORD,
    });
    conn.connect();
    return conn;
  };
})();

export async function query<ResultType = any>(
  sqlFraments: TemplateStringsArray,
  ...values: any[]
): Promise<ResultType> {
  const conn = getConn();
  return new Promise((resolve, reject) => {
    conn.query(sqlFraments.join("?"), values, (err, result) => {
      if (err) return reject(err);
      resolve(result);
    });
  });
}