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 previous chapter introduced the Result type as one option for typed error handling, alongside the try/catch and the custom error classes. This chapter takes the Result and its functional sibling Either further. They are the same idea with different names: a discriminated union that carries either a success value or a failure value, making…
A Vue component is a black box from the outside. It receives props, renders output, and emits events. The test should assert on those three things—what goes in, what comes out, and what the user sees—rather than on the internal refs, computed properties, or methods. Vue Test Utils is the library that mounts the component…
Angular components rarely live in isolation. A parent component often needs to reach into its own template and grab a reference to a child element, a directive instance, or a component. It may also need to inspect or manipulate content that a caller has projected into it via <ng-content>. Angular’s query system provides four tools…
Dependency injection in pure Dart has two dominant tools, and they solve the problem at different levels. get_it is a service locator: a container where you register instances by type and retrieve them from anywhere without passing them through constructors . injectable is a code generator that sits on top of get_it: you annotate classes,…
Docker Engine has always been a layered system. When you run docker run, the CLI talks to dockerd, which delegates to containerd, which in turn uses runc to create the actual container process . The containerd layer is the core runtime: it manages images, snapshots, and container lifecycle, and it is the component that Kubernetes…
JavaScript doesn’t stop moving. Every year, TC39 ships new features — some big, some small, all designed to remove boilerplate and fix sharp edges. Between ES2022 and the latest proposals, a set of methods and syntax has landed that most developers haven’t caught up with yet. This chapter covers what’s actually in the language now,…
The Node.js test runner is not a third-party package. It ships with the runtime, stabilized in Node.js 20, and requires no npm install for the core functionality . You write a test file, run node –test, and the runner discovers the file, executes it in a separate child process, and reports the result. The assertion…
Zustand is a small state management library for React. It does not have a provider, an action type, or a reducer. The store is a hook that returns the state and the actions, and the components call the hook and read what they need. The state lives outside the React tree, and the components subscribe…
The orphan rule is the constraint that makes Rust’s trait system coherent across independently compiled crates. Its short form is simple: you can implement your own trait for any type, you can implement any trait for your own type, but you cannot implement a foreign trait for a foreign type. The reason is link-safety and…
A savepoint is a named marker inside a transaction. It is set with the SAVEPOINT statement, and it records the state of the transaction at that point. When a later statement fails, the ROLLBACK TO SAVEPOINT returns the transaction to the marker, undoing the changes that came after it while keeping the changes that came…