错误：Route.get（）需要回调函数，但得到了一个[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)

Answer 1

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( ...

Answer 2

getAllUsers is already a function，so you can Use directly. change router.get('/users',database.getAllUsers); to router.get('/users',database); . you can yet return an object in userQueries.js file