list of programming languages
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:…
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 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…
A generic function declares its type parameters in angle brackets, and the caller chooses the concrete types. An impl Trait return type inverts that relationship: the function chooses the concrete type, and the caller is told only that the type implements a trait. The syntax is -> impl Trait, and it reads as “this function…
Two queries. Two result sets. You need the rows that appear in both. This is set intersection, and SQL provides a dedicated operator for it: INTERSECT. It is one of the three set operators in standard SQL, alongside UNION and EXCEPT. Where UNION combines results and EXCEPT subtracts one from another, INTERSECT returns only the…
Variance is the rule that decides whether a type A can be used where a type B is expected when A and B are related by subtyping. It sounds academic until you hit it in practice: you write a function that accepts a callback, pass a callback with a narrower parameter, and TypeScript rejects it….
These two media features prioritize user comfort and performance. One respects users who want less data usage, the other respects users who are sensitive to motion. Overview of Features Feature Description Values prefers-reduced-data User wants lighter data usage no-preference, reduce prefers-reduced-motion User wants less animation/motion no-preference, reduce 1. prefers-reduced-data The prefers-reduced-data media feature detects if…
A stream transformation is a function that takes a stream and returns a stream. The output stream emits values derived from the input stream’s values, and the relationship between the two is defined by the transformation. map transforms each value, where filters values, take limits the number, expand flattens each value into multiple values, and…