Updating SQL Query with JS

I have 3 HTML dropdown menus for translations, books, and chapters. The selected content of the 1st impacts the content shown on the 2nd, and the 2nd impacts the 3rd. I also need the dropdowns to update in real time so I’m using JavaScript to detect when the selections change.

I want to call this query from the page where the data will be displayed.. “SELECT DISTINCT book FROM translationTable”

I can’t nest PHP Code inside of JS, so how would I call my table using JS if I have a separate file for my DB connection? I want to try to stay as vanilla JS as possible. Thank you.

// server.js

const mysql = require('mysql');

// Create a connection to the database
const connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: '',
    database: 'myDB'
});

module.exports = connection;

// book.html
<script>
  var sql = "SELECT DISTINCT book FROM translationTable";
  result = ?;

displayContent(result);

</script>