list of programming languages
Aggregate functions collapse many rows into a single value. They answer questions like “how many orders were placed,” “what is the total revenue,” “what is the average salary,” “what is the highest price,” and “what is the earliest date.” The five standard aggregates — COUNT, SUM, AVG, MIN, and MAX — are the foundation of…
Three type operators sit at the heart of TypeScript’s type-level programming: keyof gives you the union of an object’s keys, typeof gives you the type of a value, and indexed access types (T[K]) give you the type of a property. Together they let you derive new types from existing ones — extracting keys, resolving values,…
Media queries are the foundation of responsive web design. They allow you to apply different styles based on the user’s device characteristics — screen size, orientation, resolution, and more. What are Media Queries? A media query is a CSS technique that applies styles conditionally based on the characteristics of the device or viewport. They’re defined…
A wrapper class is a useful thing. It gives a primitive a name, adds validation, and prevents an int from being passed where a UserId is expected. But a wrapper class has a cost: it allocates an object on the heap, it requires a field to hold the wrapped value, and every access goes through…
1. Basic HTML Document Structure Document Structure Elements Element Description <!DOCTYPE html> Declares HTML5 document type <html> Root element <head> Contains metadata <title> Page title (browser tab) <meta> Metadata (charset, viewport, SEO) <link> External resources (CSS, favicon) <style> Internal CSS <script> JavaScript <body> Visible content 2. Headings Best Practices: 3. Text Content Paragraphs Text Formatting…
A class is a blueprint for creating objects. It encapsulates data (properties) and functions (methods) that operate on the data. Classes provide a clean, modern syntax for object-oriented programming in JavaScript. A Quick Look at the Example a. Classes — Part 1 A class is a blueprint for creating objects. It encapsulates data (properties) and…
Express is middleware. The application itself is a middleware function, the router is a middleware function, and every route handler is a middleware function. The framework’s entire request-response pipeline is a chain of functions that receive the request, the response, and a next callback. Understanding middleware is understanding Express. The previous chapters used middleware—express.json(), logger,…
Rust has two string types, and the distinction between them is one of the first things a new Rust programmer has to internalize. A String is a growable, heap-allocated, owned sequence of UTF-8 bytes. A &str is a borrowed view into a sequence of UTF-8 bytes, usually a slice of a String or a literal…
GROUP BY partitions the rows of a result set into groups and applies aggregate functions within each group. It is the mechanism that turns a detail table into a summary table, answering questions like “how many orders per customer,” “what is the average salary per department,” or “what is the total revenue per month.” Without…
A mapped type transforms an existing type by iterating over its keys and producing a new type for each one. It’s how TypeScript’s built-in utilities like Partial<T>, Required<T>, Readonly<T>, and Pick<T, K> are implemented — and how you write your own transformations. Mapped types take the keys of one type, apply a rule to each,…