NotesToSelf.Dev

For Moment Wall Art (and other printed product sites in future), we need to show the customer not just the main print design itself but also mock-up images demonstrating how it would look in various settings.

Preamble: Introduction to interface segregation (Skip this if you’re aware of what the Interface Segration Principle is.)

A common maxim of computer security is “the attacker knows the system”.

Whether or not you’re practicing test-driven development, it’s helpful to begin writing tests with the “Given, When, Then” structure. // Given we have a queued order; // When we cancel it; // Then the order should be cancelled.

The “Specification driven development” post mentions the idea of a “a low-resistance workflow” that can be achieved with test-driven development.

Recently we were trying to set-up some network configuration to route FIX traffic from a single Docker container on a VM instance through four of our VPN gateways, two of the other side’s VPN gateways and on to two destination machines on the other side.

I’m often dealing with little bits of JSON, and sometimes it’s helpful to pretty-print them for readability.

There’s a type of small “gotcha” bug that is easy to hit with promises for boolean values in JavaScript.

A simple cause of failure in software systems is a single problematic item in a set causing the entire set to fail.

(Cross-posted from https://blog.freetrade.io/a-day-in-the-life-of-a-software-engineer-at-freetrade-a39a590d7ffa) I joined Freetrade as Senior Software Engineer in October 2018.

If you accidentally run a bash script with sh, you’re probably going to have a bad time.

Sometimes I want to manually generate a UUID for some test or example data.

Here’s a handy Python one-liner for generating a random string of letters and digits on the command line: python -c 'import random; import string; print("".join(random.choice(string.ascii_letters + string.digits) for i in range(30)))' To make it easier to

Here’s a Python one-liner for generating a random UK National Insurance Number (aka NINo) on the command line, which is useful for testing apps that use one: python -c 'import random; import string; p="ABCEGHJKLMNPRSTWXYZ"; print("".join([random.choice(p)…

One way to configure Apache Airflow is with “Variables” that can be modified programmatically or via the Airflow UI.

(Cross-posted from https://blog.freetrade.io/serverless-integration-testing-at-freetrade-5359fb0b0e57) Our tech stack at Freetrade is 99% serverless.

There’s something fun about QR codes, and I wanted an easy way generate them as SVGs.

Nodejs has a handy Promise.all function that awaits an entire batch of promises.

I’m casually going through the Japanese course in Duolingo, and found this handy wiki series on Duolingo Fandom Japanese with lists of all of the vocab.

Hugo’s taxonomies feature is very flexible and covers a lot of use cases for organising static content.

“Every comment represents a failure to make the code self explanatory.”

Given a binary tree represented sequentially as a list of integer node values, we want to identify whether the sum of the left branch or the sum of th right branch is larger.

(Cross-posted from https://blog.freetrade.io/coming-to-firebases-nosql-realtime-database-from-a-sql-background-b605b2910c4c) We use the Firebase Realtime Database at Freetrade, as part of our infrastructure on Google Cloud.

“What’s the Difference Between” is a childish word-play game where you give clues for other players to guess a spoonerism phrase pair.

A local ElasticSearch instance powers the Chinese example sentence search feature on Chinese Boost.

The catalogue data model in our 3D pop up cards shop includes Product and Tag entities.

Be careful with the S3 origin URL for a Cloudfront distribution.

I was Principal Software Engineer at Freetrade, primarily working on the platform but also some client-side work.

One of my pastimes is translating Chinese poetry and other text into English on my East Asia Student blog.

A friend mentioned a code screen interview question he likes to ask based on counting the number of discrete “islands” in a grid: Given a square grid of cells, some of which are sea (0) and some of which are land (1), implement an island counter that iden…

https://algodaily.com/challenges/count-the-planes This is the same as the island counting problem. function* enumerateGrid(grid) { if (!

Given that “implement Fizz-Buzz in a language of your choice” is quite a common programming interview task, I was wondering if it would be possible to do it in one line on the command line using Unix tools.

https://algodaily.com/challenges/contiguous-subarray-sum There’s a fairly obvious brute-force O(n^2) way to do this by looping through every possible sub-array: function sum(numbers) { return numbers.reduce((sum, x) => sum + x, 0); } function* allSubArr…

https://algodaily.com/challenges/uniqueness-of-arrays This is pretty trivial with the Set class in ECMAScript 2015. function uniques(items) { return [...new Set(items)]; } If that seems like cheating, then we can achieve this with a hash map and a new a…