Use a class method in router.get

Question

I'm really new to node.js and I'm having trouble when I'm using a class method in router.get callback
It gives me this error:
Can you guys help me out ?

Route.get() requires a callback function but got a [object object]

Here is my code

router.js :

const express = require('express');
const router = express.Router();
const test = require('../controller/controller');
router.get('/', test.testing());
module.exports = router;

controller.js :

class oop
{
    testing(req,res)
    {
        console.log('okay');
    }
}
exports.testing =new oop();

app.js :

const express = require('express');
const app = express();
app.listen(80);
const wiki = require('./routes/router');
app.use('/', wiki);

Answer 1

A callback function will be called in some arbitrary amount of time, therefore you need to provide a reference to the function... so when the time comes, Javascript can execute that function. In your case, you are not passing the function, but running it! test.testing() . What you are actually passing to the 'callback' parameter is the result of test.testing() which, in this case, is undefined