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.
An Observable has three channels: next for values, error for a terminal failure, and complete for a terminal success. The error channel is the one that is most often mishandled. Unlike next, which can fire any number of times, error fires once and terminates the stream — after it fires, no further values are emitted…
These three media features let you adapt styles based on JavaScript availability, display refresh capability, and HDR video support. Overview of Features Feature Description Values scripting Detects JavaScript availability none, initial-only, enabled update How often the display can update none, slow, fast video-dynamic-range Dynamic range of the video plane standard, high 1. scripting The scripting…
Every Dart project is a package. A package is a directory with a pubspec.yaml file, and the pubspec declares the package’s metadata, its SDK constraints, and its dependencies. The pub tool, which ships with the Dart SDK, reads the pubspec and resolves the dependency graph, downloading the required packages into a central cache and generating…
The Compose file is not a single static document. It is a base configuration, and it can be layered with override files, scoped with profiles, and merged into a final model that Compose resolves before starting any container. This layering is what allows a single repository to serve development, testing, and production without duplicating the…
ES Modules (ESM) are the official, standardized way to split JavaScript code into reusable files. They use import and export to share code between files, and they’ve replaced the older CommonJS (require/module.exports) approach in modern JavaScript. Key point: ES Modules are static — imports are resolved at load time, not runtime (except for dynamic import())….
Knex.js is a SQL query builder for Node.js. It is not an ORM, and it does not hide the SQL. It provides a fluent JavaScript API that constructs SQL queries, and the queries it produces are the SQL a developer would write by hand — but with the values parameterized, the identifiers quoted, and the…
A React component re-renders when its state changes, when its props change, or when a parent re-renders. On every re-render, the entire component function runs from top to bottom. Every variable is recreated, every computation is repeated, and every object literal is a new object. Most of the time this is fine. A few arithmetic…
Every reference in Rust has a lifetime, but most of them are never written. The compiler infers them from the code using a small set of rules called the lifetime elision rules. The rules were introduced in Rust 1.0 to reduce the noise in function signatures, and they cover the vast majority of functions. Before…
The WHERE clause is where subqueries are most common, but it is not where they are most powerful. A subquery in the SELECT list can compute a per-row value from another table. A subquery in the FROM clause can act as a temporary table, a derived table that exists only for the duration of the…
The @utility and @variant directives are the two primitives that make Tailwind v4’s CSS-first configuration work. @utility registers a custom utility class with Tailwind’s variant system, so the class supports hover:, md:, dark:, and every other variant. @variant applies a variant inside a CSS rule, replacing the @screen directive from v3 and the hover: prefix…