ehaynes99

Why TypeScript classes are a poor option for representing data

• Why TypeScript classes are a poor option for representing data
  • Example Model
  • JSON format
  • Data structure is as important as data content
  • Problems with classes as data models
    • They are incompatible with declarative syntax
    • They break type safety!
    • They promote mutation
• Decorators to the rescue cause even more problems

ehaynes99

import { sortBy, pick } from 'lodash';

/**
 * NOT A REAL IMPLEMENTATION!! This is just a high level example of how
 * dynamo stores data.
 */
type Row = {
  hashKey: string;
  rangeKey: string;
  [k: string]: any;

ehaynes99

#!/usr/bin/env node
const { exec } = require('child_process');
const { resolve } = require('path');

const cwd = process.argv[2] ? resolve(process.argv[2]) : process.cwd();
const maxBuffer = 10 * 1024 * 1024;

const execShell = (command) => {
  return new Promise((resolve) => {
    exec(command, { cwd, maxBuffer }, (error, stdout, stderr) => {

ehaynes99

type Semaphore = {
  acquire: () => Promise<void>;
  release: () => void;
};

export const simpleSemaphore = (size: number): Semaphore => {
  const waiting: (() => void)[] = [];
  let available = size;

  const acquire = async (): Promise<void> => {

ehaynes99

Workspaces Module Resolution

Originally introduced by yarn, starting with version 7 npm also provides support for this.

What is it?

Workspaces are first-class support in the package manager for monorepo structures in npm packages. A monorepo is simply a collection of related packages, and having them share a single git repo can help eliminate a lot of redundancy in the project setup, as well as make it easier to work with interdependencies during development.

What does a workspaces project look like?

They're relatively simple. They consist of:

• a parent directory whose package.json contains a list (or wildcard pattern) defining subprojects

ehaynes99

Critique of NestJS

Here, I am going to examine NestJS -- primarily focusing on its dependency injection --

The basics

Nest's DI system is based on a custom-defined module system. For every service defined in the application, there is a module file that "owns" that service. I use the term "service" loosely here to simply mean "anything we want to be part of the DI system". For example:

@Injectable()

ehaynes99

Nuke the world!!!!!

# kill anything running
docker kill $(docker ps -q)
docker system prune -af --volumes # aka --all --force --volumes

ssh

docker exec -it  /bin/bash

ehaynes99

Debugging TypeScript with ts-node in VSCode

These launch configs will allow you to debug typescript files directly from VSCode. It will honor the tsconfig and resolve node modules properly. You do not need to install ts-node or nodemon, as everything is run using npx. The first

Launch Config

{
  "configurations": [
    {
      "type": "node",
      "request": "launch",

ehaynes99

ehaynes99

/* eslint-disable @typescript-eslint/no-misused-promises */
import { Readable, Transform, Writable } from 'node:stream'
import { pipeline } from 'node:stream/promises'

export const asyncHandler = (handle: (value: any) => Promise<void>) => {
  return new Writable({
    objectMode: true,
    write: async (value, _, next) => {
      try {
        await handle(value)