问使用express.js返回未定义的MySQL存储过程

EN

var express = require('express');
var router = express.Router();
var mysql = require('mysql');
var bcrypt = require('bcrypt');
//constants
const tableName = 'user';

var connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: '',
    database: 'users',
    charset : 'utf8mb4'
});

//function to insert to or retrieve data from the database
router.post('/', function(req, res, next) {
        let userID = req.body.userID;
        connection.query(
            "CALL `getUsers`(?)",
                [userID],
                function(err, row, field) {
                if (err) {
                    res.send({ 'success': false, 'message': 'Could not connect. ' + err});
                }
                if ( row.length > 0 ) {
                    console.log('name: ' + row[0].name);
                    res.send({ 'success': true, 'users': row });
                } else {
                    res.send({ 'success': false, 'message': 'No users found.' });
                }
        }); 
    }
});