Unnesting Node database calls

Question

I have an ordinary

var express = require(\'express\')

Node express www page, using session, pug, etc as usual. My db calls

var         


        

Answer 1

Simply convert the mysql functions into promises using the nodejs standard lib util.promisify

example:

const { promisify } = require('util');

const catsPromise = promisify(db.cats);
const dogsPromise = promisify(db.dogs);
const budgiesPromise = promisify(db.budgies);

async function routeHandler() {
  let err = null;

  try {
    const cats = await catsPromise();
    const dogs = await dogsPromise();
    const budgies = await budgiesPromise();
  } catch(error) {
    err = error;
  }

  if (err) {
    console.log(err);
    // you should res.end() or res.render(someErrorPage) here
    // failure to do so will leave the request open
  } else {
    res.render('bigScreen.pug', {
      'cats' : cats,
      'k9s': dogs,
      'budgies': budgies,
      'pretty' : true
    });
  }
}