ReferenceError: error is not defined when pass callback parameter

Question

When I try call a callback method my parameters is not defined, only when a callback function is previous defined. What is the correct way to pass parameters to a previous declarated method?

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : 'root',
  database : 'database'
});

function doQuery(query, callback){
  connection.connect();
  connection.query(query, callback(error, results,fields)); 
  connection.end();
}

doQuery('SELECT 1 + 1 AS sum', function (){
  if (error) throw error;
  console.log(results[0].sum);
})

ReferenceError: error is not defined
    at doQuery (/home/usr/workspace/project/code.js:11:36)
    at Object.<anonymous> (/home/usr/workspace/project/code.js:15:1)
    at Module._compile (module.js:643:30)
    at Object.Module._extensions..js (module.js:654:10)
    at Module.load (module.js:556:32)
    at tryModuleLoad (module.js:499:12)
    at Function.Module._load (module.js:491:3)
    at Function.Module.runMain (module.js:684:10)
    at startup (bootstrap_node.js:187:16)
    at bootstrap_node.js:608:3

Jorge Mejia · Accepted Answer · 2018-01-23 15:12:53Z

1

You have to return your callback like this:

function doQuery(query, callback){
    connection.query(query, (error, results, fields)=> {
         callback(error, results, fields);
    })
}

answered Jan 23, 2018 at 15:12

Jorge Mejia

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Prakash Naidu · Accepted Answer · 2018-01-23 15:06:53Z

1

need to add error argument function(error){ so that it can available inside function

doQuery('SELECT 1 + 1 AS sum', function (error){
      if (error) throw error;
      console.log(results[0].sum);
    })

answered Jan 23, 2018 at 15:06

Prakash Naidu

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