问在express应用程序中，公共文件夹中的javascript文件如何访问写在index.js下的routes文件夹中的数据库API

EN

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

var connection = mysql.createConnection({
    'host':'localhost',
    'user':'root',
    'password':'',
    'database':'displayu'
});

connection.connect();

/* GET home page. */
router.get('/', function(req, res, next) {
  res.render('index');
});


router.get('/getusers',function(req,res,next){
    var x;
    connection.query('SELECT * FROM sample', function(err,result,field){
        if (err){
            throw error;
        }
        else{
            x = res.json(result);
            console.log(x);
        }
    });

});
module.exports = router;