Tutorials covering programming languages, type systems, architecture, tooling, and the patterns used to build software that lasts. Each chapter is standalone, built around real examples and verified facts.
The UNION operator combines the result sets of two or more SELECT statements into a single result set. Unlike a join, which combines columns from two tables side by side, a union combines rows from two queries one after another. The two queries must have the same number of columns, the corresponding columns must have…
![Tailwind CSS 40 🎨 Arbitrary Variants and Grouped Variant Syntax ([&:nth-child(3)]:)](https://tuts.kandz.me/wp-content/uploads/2026/10/Screenshot_20261009_120535-767x665.jpeg)
Tailwind’s built-in variants — hover:, md:, dark:, group-hover: — cover the common cases. But they cannot cover every case. What if you need to style the third item in a list? What if you need to target a child element that has no class of its own? What if you need to apply a utility…
Every type system answers one question the same way: is this value assignable to that type? The answer depends on whether the system is structural — comparing shapes — or nominal — comparing names. TypeScript is structural. { x: number; y: number } is compatible with any other type that has x: number and y:…
The declarative model in Vue abstracts away the direct DOM manipulation for most cases, but there are times when you need the actual element. You need to focus an input when the component mounts. You need to measure the height of a div to set the scroll position. You need to pass a DOM node…
The previous two chapters introduced Observables and the transformation and filtering operators. This chapter is about the four operators that cause the most confusion and produce the most bugs in Angular code: switchMap, mergeMap, concatMap, and exhaustMap. They share a signature — a function from a value to an Observable — but they handle concurrency…
These two media features are essential for accessibility and personalization. They let you respect the user’s preferred color scheme (light/dark) and contrast level. Overview of Features Feature Description Values prefers-color-scheme User’s preferred color scheme light, dark prefers-contrast User’s preferred contrast level no-preference, more, less, custom 1. prefers-color-scheme The prefers-color-scheme media feature detects whether the user…
A StreamController is the object that creates a stream and gives you the methods to add events to it. It is the most flexible way to create a stream, because it gives the producer full control over when values are emitted, when errors are added, and when the stream is closed. The controller has a…
The Compose specification is the schema that defines what a compose.yaml file can contain. It is not a Docker-specific format; it is an open specification that Docker Compose, Docker Swarm (partially), and other tools implement. The specification defines the top-level elements — services, networks, volumes, configs, secrets, and the project-level settings — and the sub-elements…
The spread operator (…) takes an iterable — an array, a string, a Set, a Map — or an object, and expands its contents into individual elements. It’s the opposite of the rest parameter, which collects values into an array. Same syntax, different purpose. Key point: Spread expands; rest collects. Both use …, and the…
SQL injection is the most persistent vulnerability in web applications. It has been in the OWASP Top 10 since the list was created, and it remains there because the underlying mistake is so easy to make. The mistake is string concatenation: building a query by pasting user input into a template. The input is treated…