Why doesn't push move results from DB query into variable?

Question

Intent

Establishing a connection with a DB in my route, running a query, capturing the result, and making it accessible to my index view to render in the DOM.

Problem

DB connects and returns results successfully in the console. However, fails to push this result into the "finalResult" array.

var express = require('express');
var router = express.Router();

router.get('/', function(req, res) {

// Establish Connection with Database
var mysql = require('mysql');
var connection = mysql.createConnection({
    host : '127.0.0.1',
    user : 'root',
    password : 'xxxxxxx',
    database : 'my_db'
});

connection.connect();

// // Query and post result to console
connection.query('SELECT * FROM products', function(error, results, fields) {
    if (error) throw error;
    doSomething(results[0]);
});

connection.end();


var finalResult = ['hello'];

function doSomething(results) {
    console.log(results.name);
    finalResult.push(results.name);
}

console.log(finalResult);


// Render/make accessible to views
res.render('index', {
    pageTitle: 'Home',
    result: finalResult
});
});

module.exports = router;

doSomething(results[0]); successfully pushes the result into the doSomething() function because console.log(results.name) returns the correct query result. Issue occurs with finalResult.push(results.name) because console.log(finalResult) only returns an array with "hello" when it should have "hello" plus the query result.

Mudzia Hutama · Accepted Answer · 2021-05-27 19:02:59Z

1

Please note when you query database from mysql module is synchronous (the query takes function as argument -- callback). That's mean you cannot take result value as variable outside the query function. Try to use async/await or promise to get returned value.

answered May 27, 2021 at 19:02

Mudzia Hutama

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Comments

Sari · Accepted Answer · 2017-03-25 21:06:19Z

0

Try to write console.log(finalResult) inside doSomething function, after you pushed the new data to finalResult array.

I think that you see only "helo" because console.log(finalResult) execute before the doSomething function finished (before you add the data to finalResult array).

answered Mar 25, 2017 at 21:06

Sari

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2 Comments

lookininward Over a year ago

Yup, that does work. Though I'm still confused.. how can I get it to execute doSomething() first? I want to be able to pass the results into the res.render function.

Sari Over a year ago

You can move the res.render..... to the connection.query function, right after the calling to doSomething function or add a function for the res.rende and call this function right after doSomething function.

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