I can't accomplish async and await in order to populate array and then show the end result.
When I execute the code, firstly there is an empty array. When I go "refresh", then data is populated.
Obviously async. But I don't know how to write the code
The similar problem is described here
https://community.apigee.com/questions/49199/nodejs-cache-retrieve-data-and-push-to-array.html

My code so far

const express = require('express');
const router = express.Router();
const db = require('../../config');
var async = require('async');

function readDb(nameOfTableInDb, someArray) {
// reuse a conneciton to db
    db.getConnection(function (err, conn) {
        if (err) {
            res.json({ "code": 100, "status": "Error in connection DB..." });
            return;
        }
        let qry = "";
        switch (nameOfTableInDb) {
            case "tblcategories": {
                qry = "SELECT DISTINCT c.catName, (select COUNT(*) from tblPostCatMap as pp where pp.idcat = c.idcategorie) as summeCat from " + nameOfTableInDb + " as c order by c.catName asc";
                break;
            }
            case "tblsubcat": {
                qry = "SELECT DISTINCT c.subCatName, (select COUNT(*) from tblPostCatMap as pp where pp.idSubCat = c.idSubCat) as summeSubcat from " + nameOfTableInDb + " as c order by c.subCatName asc";
                break;
            }
        }
        conn.query(qry, function (error, rows) {
            if (error) {
                throw error;
            }
            // add results from DB to someArray array
            someArray.push(rows);
        });
        conn.release();
    });
    return someArray;
}
router.get('/', function (req, res, next) {
    var someArray = [];
    var run = async() => {
        const data = await readDb("tblcategories", someArray);
        const data = await readDb("tblsubcat", someArray);
        console.log("async result:\n" + data);
    }
    run();
});

Solved like this.

async function showAllFilters(qry, arrayParams) {
    // params is array[]
    let result;
    try {
        result = await db.query(qry, arrayParams);

    } catch (error) {
        console.log("showAllFilters error: ");
        console.error(error);
    }
    return result;
}

router.get('/', function (req, res) { // localhost:5000/api/filter
    let qry = "SELECT DISTINCT c.subCatName, (select COUNT(*) from tblPostCatMap as pp where pp.idSubCat = c.idSubCat) as subcatSumme from tblsubcat as c order by c.subCatName asc";
    showAllFilters(qry,[])
    .then(r => { // first, you get the count of records of all posts and store into count var
        var rows = [];
        rows.push(r); // 357 
        // do the rest of pagination
        qry = "SELECT DISTINCT c.catName, (select COUNT(*) from tblPostCatMap as pp where pp.idCat = c.idCategorie) as catSumme from tblcategories as c order by c.catName asc";
        showAllFilters(qry, [])
        .then(r2 => {
            rows.push(r2);
            res.render('filter', { rows });
        })
        .catch(err => {
            console.log("Err in showing all posts with pagination: " + err);
        });
    })
    .catch(err => {
        console.log("Err in getting the count of all posts: " + err);
    });
});
module.exports = router;