js ajax查询数据库

function loadData() {
    var xhttp = new XMLHttpRequest();
    xhttp.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {
            document.getElementById("demo").innerHTML = this.responseText;
        }
    };
    xhttp.open("GET", "/queryDatabase?param=value", true);
    xhttp.send();
}

const express = require('express');
const app = express();
const mysql = require('mysql');

const connection = mysql.createConnection({
    host: 'localhost',
    user: 'user',
    password: 'password',
    database: 'database_name'
});

app.get('/queryDatabase', (req, res) => {
    const param = req.query.param;
    connection.query('SELECT * FROM table_name WHERE column = ?', [param], (error, results) => {
        if (error) throw error;
        res.send(JSON.stringify(results));
    });
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});