如何将sql查询变量添加到javascript中并进行计算？

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.use(express.json());

app.post('/api/query', (req, res) => {
  const sql = req.body.sql;
  connection.query(sql, (error, results) => {
    if (error) throw error;
    res.json(results);
  });
});

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

document.getElementById('queryButton').addEventListener('click', async () => {
  const sqlQuery = document.getElementById('sqlInput').value;
  try {
    const response = await fetch('/api/query', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json'
      },
      body: JSON.stringify({ sql: sqlQuery })
    });
    const data = await response.json();
    // 进行计算
    const result = data.reduce((acc, val) => acc + val.someField, 0);
    console.log('计算结果:', result);
  } catch (error) {
    console.error('Error:', error);
  }
});

app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');
  next();
});

connection.query('SELECT * FROM users WHERE id = ?', [userId], (error, results) => {
  // ...
});