Error: Route.get() requires a callback function but got a [object Undefined] NODE.JS + SQL

Question

I would like to separate the router.get () from queries from sql queries, but I had this error, when I declare the direct function as parameter of router.get () function it works.

User.js

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

const database = require('../queries/userQueries');

router.get('/users',database.getAllUsers);

module.exports = router;

userQueries.js

function getAllUsers(req, res, next) {
    res.locals.connection.query('SELECT * from usuarios', 
    function (error, results, fields) {
        if (error){ 
            res.send(error); 
            return; 
        }
        res.send(results);
    });
};

module.exports = getAllUsers;

Error: Route.get() requires a callback function but got a [object Undefined] at Route.(anonymous function) [as get] (/home/antonio/achaiAPI/node_modules/express/lib/router/route.js:202:15) at Function.proto.(anonymous function) [as get] (/home/antonio/achaiAPI/node_modules/express/lib/router/index.js:510:19) at Object. (/home/antonio/achaiAPI/api/routes/user.js:11:8) at Module._compile (internal/modules/cjs/loader.js:678:30) at Object.Module._extensions..js (internal/modules/cjs/loader.js:689:10) at Module.load (internal/modules/cjs/loader.js:589:32) at tryModuleLoad (internal/modules/cjs/loader.js:528:12) at Function.Module._load (internal/modules/cjs/loader.js:520:3) at Module.require (internal/modules/cjs/loader.js:626:17) at require (internal/modules/cjs/helpers.js:20:18)

CertainPerformance CertainPerformance · Accepted Answer · 2018-06-12T03:26:30

You're assigning the function getAllUsers itself to the module.exports, not to a property of module.exports. So, when you import it with require, that resolves to said function, not an object with that function as one of its properties.

Try assigning the imported object to a variable name representing the function instead:

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

const getAllUsers = require('../queries/userQueries');

router.get('/users', getAllUsers);

module.exports = router;

You would use

const database = require('../queries/userQueries');
router.get('/users',database.getAllUsers);

when your userQueries.js had assigned the function to a property of the exports:

module.exports.getAllUsers = function getAllUsers( ...

Error: Route.get() requires a callback function but got a [object Undefined] NODE.JS + SQL

2 Answers