CODEWITHSUNDEEP
mysqlnode.jsexpress
Renee
Renee

Reputation: 29

why can't I get the results of the query

I seperate the sql query and router file into two, trying to apply MVC concept. But why can I pass the result of the query? it doesn't work now, the console printed "undefine" instead of the results

//homeapi.js under folder api
var mysql = require('../conf/db');
let getAll = {};
getAll.all = () => {
    var userGetSql = 'SELECT * FROM product';
    mysql.query(userGetSql, (err, results) => {
      if (err) {
        return ;
      }
      return results;
    })
}

let info = getAll.all();
console.log(info)

module.exports = getAll;

//index.js under routers file,  I try to import it, but also failed
var getAll = require('../api/homeapi');
router.get('/product', (req,res,next) => {
  res.json(getAll.all());
});

Upvotes: 0

Views: 35

Answers (1)

Nir Levy
Nir Levy

Reputation: 12953

NodeJS works asynchronously, which means when you call res.json(getAll.all()); the res.json is executed before the query execution ends.

The correct way to do it is:
1. your getAll function should get a callback from outside (just like the mysql function does)
2. the router function should pass a callback to the getAll and in it pass the result to the response

getAll.all = (callback) => {
    var userGetSql = 'SELECT * FROM product';
    mysql.query(userGetSql, callback);
}

router.get('/product', (req,res,next) => {
  getAll.all((result, err) => {
    if (err) {
       return res.json('some error message');
    }
    return res.json(result);
  });
});

Upvotes: 1

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