How to get, use, and close a DB connection using promises

db-config.js

module.exports = {
  user: 'hr',
  password: 'oracle',
  connectString: 'localhost:1521/orcl',
  poolMax: 20,
  poolMin: 20,
  poolIncrement: 0
};

employees.js

const oracledb = require('oracledb');

function getEmployee(empId) {
  return new Promise(function(resolve, reject) {
    let conn; // Declared here for scoping purposes.

    oracledb
      .getConnection()
      .then(function(c) {
        console.log('Connected to database');

        conn = c;

        return conn.execute(
          `select *
          from employees
          where employee_id = :emp_id`,
          [empId],
          {
            outFormat: oracledb.OBJECT
          }
        );
      })
      .then(
        function(result) {
          console.log('Query executed');

          resolve(result.rows[0]);
        },
        function(err) {
          console.log('Error occurred', err);

          reject(err);
        }
      )
      .then(function() {
        if (conn) {
          // If conn assignment worked, need to close.
          return conn.close();
        }
      })
      .then(function() {
        console.log('Connection closed');
      })
      .catch(function(err) {
        // If error during close, just log.
        console.log('Error closing connection', e);
      });
  });
}

module.exports.getEmployee = getEmployee;

index.js

const oracledb = require('oracledb');
const dbConfig = require('./db-config.js');
const employees = require('./employees.js');

oracledb.createPool(dbConfig)
  .then(function() {
    return employees.getEmployee(101);
  })
  .then(function(emp) {
    console.log(emp);
  })
  .catch(function(err) {
    console.log(err);
  });

package.json

{
  "name": "promises",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "Dan McGhan <dan.mcghan@oracle.com> (https://jsao.io/)",
  "license": "ISC",
  "dependencies": {
    "oracledb": "^1.13.1"
  }
}

This gist is a demo app that shows how to get, use, and close a DB connection using promises. See the related blog post and the main post for the series for more details.

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