mysql - Error "message": "db is not defined" node

Question

I'm creating an MVC API with MySQL and node and I got this error while testing with postman.

All the functions are inside class DBConnection();

Initialising Connection

const mysql2 = require("mysql2");
require("dotenv").config();

class DBConnection {
  constructor() {
    this.db = mysql2.createPool({
      host: process.env.DB_HOST,
      user: process.env.DB_USER,
      password: process.env.DB_PASS,
      database: process.env.DB_DATABASE,
    });

Checking errors

    this.checkConnection();
  }

  checkConnection() {
    this.db.getConnection((err, connection) => {
      if (err) {
        if (err.code === "PROTOCOL_CONNECTION_LOST") {
          console.error("Database connection was closed.");
        }
        if (err.code === "ER_CON_COUNT_ERROR") {
          console.error("Database has too many connections.");
        }
        if (err.code === "ECONNREFUSED") {
          console.error("Database connection was refused.");
        }
      }
      if (connection) {
        connection.release();
        console.log ("connected to db");
      }
      return;
    });
  }

Query

  async query(sql, values) {
    console.log("++++++++++", this.db);
    return new Promise((resolve, reject) => {
      const callback = (error, result) => {
        if (error) {
          console.log(error)
          reject(error);
          return;
        }
        resolve(result);
      };
      // execute will internally call prepare and query
      this.db.execute(sql, values, callback);
    }).catch((err) => {
      const mysqlErrorList = Object.keys(HttpStatusCodes);
      // convert mysql errors which in the mysqlErrorList list to http status code
      err.status = mysqlErrorList.includes(err.code)
        ? HttpStatusCodes[err.code]
        : err.status;

      throw err;
    });
  }
}

// like ENUM
const HttpStatusCodes = Object.freeze({
  ER_TRUNCATED_WRONG_VALUE_FOR_FIELD: 422,
  ER_DUP_ENTRY: 409,
});

module.exports = new DBConnection().query;

From the response, I got error code 500 Internal Server Error. I'm assuming the error is resulting from the constructor, but any suggestions are welcomed.

question from:https://stackoverflow.com/questions/65949045/error-message-db-is-not-defined-node

Answer 1

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