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Creating E-Invoices with Free and Open Source Software

Starting 1 January 2025, electronic invoicing will become mandatory for all B2B transactions in Germany. Several other countries in the European Economic Area have already adopted similar requirements, or will soon follow suit. As a result, many businesses in Germany are racing to implement electronic invoicing solutions, though many face challenges along the way. Discover how you can simplify this process by generating electronic invoices in multiple formats — using only free and open-source software.

Hidden Quirks of JavaScript `for...in` Loops

The C-style three-expression for loop in JavaScript is often viewed as old school or awkward beginner style. Some developers automatically use a for...of, foreach, or for...in statement instead. But the latter has a subtle pitfall that can lead to unexpected behaviour.

Abusing JSON.stringify()

Abusing JSON.stringify is very popular in the JavaScript world but many people fail to see the limitations and hidden dangers of using JSON.stringify() for things that it was not made for. This blog post is actually about how to avoid this and use the right tools instead.

The Easiest Method to Solve the Rubik's Cube

There are quite a few similar tutorials on the internet that show you how to solve the cube with just one algorithm. But this one is part 1 of a from-zero-to-hero series of posts that will show you how to evolve this simple method into the preferred method of solving the cube that most leading speed cubers use. Besides, it neatly visualises all steps so that you don't have to learn the cube notation from the beginning.

Yargs 18 Pitfalls

Upgrading Yargs from version 17 to 18 in a TypeScript project using Jest turned out to be a bit of a nightmare. The release notes for Yargs 18.0.0 include the line “yargs is now ESM first” — a seemingly small change that can cause major headaches. In this blog post, we’ll take a closer look at what that means and how to deal with it.

Miscellaneous • Aug 14th '26

Change Grundfos PM 2 Pressure Monitor Cable

The Grundfos PM 2 pressure control unit is used to automatically switch water pumps on and off. The electrical connection to the pump is made using a Schuko (type F) plug connection. In my case, this connection had burned out and I had to replace it. This blog post describes how to do it.

Pirate ship — Photo by Elena Theodoridou on Unsplash

Development • Oct 8th '25

Yargs 18 Pitfalls

A stylish cube — Photo by aaron boris on Unsplash

Miscellaneous • Jun 23rd '25

The Easiest Method to Solve the Rubik's Cube

Carpentry Tools — Photo by Étienne Girardet on Unsplash

Development • Nov 21st '24

Abusing JSON.stringify()

Upper part of a ferris-wheel at night — Photo by Yunus Emre on Unsplash

Development • Nov 12th '24

Hidden Quirks of JavaScript `for...in` Loops

Development • Nov 4th '24

Creating E-Invoices with Free and Open Source Software

Original photo by Pierre Bamin on Unsplash

Development • May 16th '24

Dynamic Angular Configuration

Development

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Development • Oct 8th '25

Yargs 18 Pitfalls

Development • Nov 12th '24

Hidden Quirks of JavaScript `for...in` Loops

Development • Nov 4th '24

Creating E-Invoices with Free and Open Source Software

Development • Nov 21st '24

Abusing JSON.stringify()

Development • May 16th '24

Dynamic Angular Configuration

Development • May 9th '24

Compiling ImageMagick for Perl

Development • Mar 28th '24

Standalone Angular Tour Of Heroes

Development • Mar 7th '24

Authenticating Access to Private Content Hosted with AWS CloudFront

Development • Jan 28th '24

Pitfalls in Testing NestJS Modules using HttpService

Development • Sep 4th '23

Platform-Independent Asynchronous Child Process IPC

DevOps

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Metal padlock on keyboard — Photo by Towfiqu barbhuiya on Unsplash

Development • Mar 7th '24

Authenticating Access to Private Content Hosted with AWS CloudFront

Setting up a static website, uploading it into an S3 bucket that serves as the origin of a CloudFront distribution is a simple and cheap solution. But what if you want to control access to the content? HTTP basic authentication no longer seems to work and is clumsy and ugly anyways. But signed cookies give you a better solution at hand and it is easy to implement with serverless computing.

Passwords on post-it attached to monitor

DevOps • Feb 12th '19

How to Use Saved Passwords Everywhere

Some web sites and applications prevent users from using previously saved credentials. There a very few legitimate reasons to do so. In the vast majority of cases, such measures just patronize users, often those people that actually keep up the service with their financial support. But it is actually quite simple to bypass such paranoid settings.

Development • May 9th '24

Compiling ImageMagick for Perl

DevOps • Jun 10th '17

Simple Single Sign-On Part 1 - (Open)LDAP

Individual user and password databases for every single service in a network are a nuisance for users and for admins, especially when users have a tendency of forgotting their password. Using LDAP for a centralized user management is less complicated than you might think. Even in a SOHO (Small Office/Home Office) environment LDAP is not overkill. Setting it up will pay out in little time.

DevOps • Dec 2nd '19

Postfix, Amavis, and ClamAV Extremely Slow

DevOps • Aug 9th '18

Syslog-ng Unique Persist Names

DevOps • Sep 14th '16

Group Authentication For Nginx

DevOps • Feb 29th '16

Simple Content Negotiation For Nginx

DevOps • Feb 27th '16

Multilingual Web Sites with Jekyll

DevOps • Feb 16th '16

Simple Dynamic DNS

Food

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Recipes • Jun 24th '21

Fruity Green Lentils Oriental Style

Lentils can be combined with pretty much everything. The combination with fruit has been on my list for a long time already. I wanted to go with pomegranate seeds that I could not dig up, however. So I tried it with the goji berries that have been lying around in my pantry for at least a year.

Recipes • Jun 4th '21