CRUD with nodejs, MySQL, and express

api.js

//requires
var mysql = require('mysql');
const express = require("express");
const app = express();
const { apiHost, apiPort, apiKey, mysqlSettings } = require('./config.json');

//web server
app.listen(apiPort, apiHost, () => {
    console.log("Application started and listening on http://" + apiHost + ":" + apiPort);
});

//mysql
var pool = mysql.createPool({
    connectionLimit: mysqlSettings.connectionLimit,
    host: mysqlSettings.host,
    user: mysqlSettings.user,
    password: mysqlSettings.password,
    database: mysqlSettings.database
});

//create
app.get("/insert/:table/:authkey", (req, res) => {
    let table = req.params.table;
    let authkey = req.params.authkey;
    if (authkey !== apiKey) {
        res.send('API Key is invalid.')
    } else {
        let keyString = '';
        let valString = '';
        for (var key in req.query) {
            keyString += key + ', ';
            valString += req.query[key] + ', ';
        }
        keyString = keyString.slice(0, -2);
        valString = valString.slice(0, -2);
        pool.getConnection(function (err, connection) {
            connection.query(
                "INSERT INTO " + table + " (" + keyString + ") VALUES (" + valString + ")",
                function (err, results, fields) {
                    if (err) {
                        console.log(err);
                        res.send();
                    } else {
                        res.send(JSON.stringify(results));
                    }
                }
            );
        });
    }

});

//read
app.get("/select/:table/:authkey", (req, res) => {
    let table = req.params.table;
    let authkey = req.params.authkey;
    if (authkey !== apiKey) {
        res.send('API Key is invalid.')
    } else {
        pool.getConnection(function (err, connection) {
            connection.query("SELECT * FROM " + table, function (err, rows) {
                connection.release();
                if (err) {
                    console.log(err);
                    res.send();
                } else {
                    res.send(JSON.stringify(rows));
                }
            });
        });
    }
});

//update
app.get("/update/:table/:id/:authkey", (req, res) => {
    let table = req.params.table;
    let id = req.params.id;
    let authkey = req.params.authkey;
    if (authkey !== apiKey) {
        res.send('API Key is invalid.')
    } else {
        let updateString = '';
        for (var key in req.query) {
            updateString += key + "='" + req.query[key] + "', ";
        }
        updateString = updateString.slice(0, -2);
        pool.getConnection(function (err, connection) {
            connection.query(
                "UPDATE " + table + " SET " + updateString + " WHERE id = " + id + ";",
                function (err, results, fields) {
                    if (err) {
                        console.log(err);
                        res.send();
                    } else {
                        res.send(JSON.stringify(results));
                    }
                }
            );
        });
    }
});

//delete
app.get("/delete/:table/:id/:authkey", (req, res) => {
    let table = req.params.table;
    let id = req.params.id;
    let authkey = req.params.authkey;
    if (authkey !== apiKey) {
        res.send('API Key is invalid.')
    } else {
        pool.getConnection(function (err, connection) {
            connection.query(
                "DELETE FROM " + table + " WHERE id='" + id + "'",
                function (err, results, fields) {
                    if (err) {
                        console.log(err);
                        res.send();
                    } else {
                        res.send(JSON.stringify(results));
                    }
                }
            );
        });
    }
});

config.json

{
	"apiHost": "localhost",
	"apiPort": 4000,
	"apiKey": "W7S5Lk8JMBb457e9JRFbRzCRHHB5Zh5N3vnnLLhDuKPDLBzXWBSsfNJ8rUnbKaRuCFp2", //set this to any random string to use for your api endpoint
	"mysqlSettings": {
		"connectionLimit": 10,
		"host": "localhost",
		"user": "someuser",
		"password": "somepassword",
		"database": "somedatabase"
	}
}