thebopshoobop

const display = (res, items) => {
  let lines = [];
  items.forEach(item => {
    lines.push("<hr>");
    lines.push([`${item.name}: $${item.price}`]);
  });
  lines = lines.join("<br>");
  res.writeHead(200, { "Content-Type": "text/html" });
  res.end(lines);
};

thebopshoobop

const opts = {
  most: () => [{}, {}, { sort: { price: -1 } }],
  least: (most) => [{ category: most.category }, {}, { sort: { price: 1 } }],
  sum: (most, least) => {
    return [
      [
        {
          $match: {
            category: most.category,
            _id: { $nin: [most._id, least._id] }

thebopshoobop

app.get("/callback", (req, res) => {
  const errCall = e => {
    res.status(500).end(e.stack);
  };
  Product.findOne(...mostOpts(), (err, most) => {
    if (err) return errCall(err);
    Product.findOne(...leastOpts(most), (err, least) => {
      if (err) return errCall(err);
      Product.aggregate(...sumOpts(most, least), (err, sum) => {
        if (err) return errCall(err);

thebopshoobop

Product.findOne(...mostOpts())
  .then(most => {
    Product.findOne(...leastOpts(most))
      .then(least => { //... })
    // ...

thebopshoobop

Product.findOne(...mostOpts())
 .then(most => {
    return Promise.all([ most, Product.findOne(...leastOpts(most)) ]);
  })
  .spread(most, least => { //... })
  // ...

thebopshoobop

app.get("/promise", (req, res) => {
  let most;
  let least;
  Product.findOne(...mostOpts())
    .then(m => {
      most = m;
      return Product.findOne(...leastOpts(most));
    })
    .then(l => {
      least = l;

thebopshoobop

app.get("/async", async (req, res) => {
  try {
    const most = await Product.findOne(...mostOpts());
    const least = await Product.findOne(...leastOpts(most));
    const sum = await Product.aggregate(...sumOpts(most, least));
    display(res, [most, least, sum[0]]);
  } catch (e) {
    res.status(500).end(e.stack);
  }
});

thebopshoobop

// non-sequential actions
const promises = [ Product.find(), Category.find() ]

// handling with plain promises
Promise.all(promises)
  .spread((products, categories) => {
    doLiterallyAnything(products, categories)
  });
  
// handling with await

thebopshoobop

const mongoose = require("mongoose");
const Schema = mongoose.Schema;
const uniqueValidator = require("mongoose-unique-validator");
const bcrypt = require("bcrypt");

const UserSchema = new Schema({
  username: { type: String, required: true, unique: true },
  passwordHash: { type: String, required: true }
});

thebopshoobop

const passport = require("passport");
app.use(passport.initialize());
app.use(passport.session());