Promise-Wrapper.md

Promise wrappers

In addition to errback interface there is thin wrapper to expose Promise-based api

Basic Promise

/* eslint-env es6 */
const mysql = require('mysql2/promise'); // or require('mysql2').createConnectionPromise
mysql.createConnection({ /* same parameters as for non-promise createConnection */ })
  .then(conn => conn.query('select foo from bar'))
  .then(([rows, fields]) => console.log(rows[0].foo));

const pool = require('mysql2/promise').createPool({}); // or require('mysql2').createPoolPromise({}) or require('mysql2').createPool({}).promise()
pool.getConnection()
  .then(conn => {
    const res = conn.query('select foo from bar');
    conn.release();
    return res;
  }).then(result => {
    console.log(result[0][0].foo);
  }).catch(err => {
    console.log(err); // any of connection time or query time errors from above
  });

ES7 Async Await

async function example1 () {
  const mysql = require('mysql2/promise');
  const conn = await mysql.createConnection({ database: test });
  const [rows, fields] = await conn.execute('select ?+? as sum', [2, 2]);
  await conn.end();
}

async function example2 () {
  const mysql = require('mysql2/promise');
  const pool = mysql.createPool({database: test});
  // execute in parallel, next console.log in 3 seconds
  await Promise.all([pool.query('select sleep(2)'), pool.query('select sleep(3)')]);
  console.log('3 seconds after');
  await pool.end();
}

With CO

const mysql = require('mysql2');
const co = require('co');
co(function * () {
  const c = yield mysql.createConnectionPromise({user: 'root', namedPlaceholders: true });
  const rows = yield c.query('show databases');
  console.log(rows);
  console.log(yield c.execute('select 1+:toAdd as qqq', {toAdd: 10}));
  yield c.end();
});

Examples in /examples/promise-co-await