Tutorials covering the frameworks and libraries that shape how modern applications are built — Angular, React, Vue, and the ecosystem tools that surround them. Each chapter is standalone, built around real examples and verified facts.
Utility-first CSS has a well-known friction point. When the same set of utilities appears on every instance of a component — a button, a card, a badge — the markup is repeated, and a change to the pattern requires editing every occurrence. The @apply directive is Tailwind’s answer. It takes a list of utility classes…
A component that loads data asynchronously has three states: loading, loaded, and failed. The traditional way to handle these is a v-if chain: show a spinner while loading is true, show the content when data is present, and show an error when error is set. Every component repeats this pattern, and every parent repeats the…
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…
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…
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…
A modal dialog has a layout problem. It needs to appear centered on the screen, above everything else, with a backdrop that covers the entire page. If the modal is rendered inside a deeply nested component, its parent’s CSS can interfere: an overflow: hidden, a transform, a z-index stacking context, or a position: relative ancestor….
Every Observable in RxJS is either cold or hot, and the distinction determines what happens when more than one subscriber arrives. A cold Observable creates a new producer for each subscriber — two subscribers to an HTTP call send two requests, and two subscribers to an interval create two timers. A hot Observable shares a…
useCallback is the function-specific version of useMemo. It returns a memoized function that only changes identity when its dependencies change. The comparison is the same: on every render, React compares the dependency array, and if the dependencies are unchanged, it returns the same function reference from the previous render. If a dependency has changed, it…
The @plugin directive is Tailwind v4’s mechanism for loading JavaScript-based plugins in a CSS-first configuration. In v3, plugins were registered in the plugins array of tailwind.config.js. In v4, the configuration moves to CSS, and the @plugin directive is the replacement. It loads a plugin from a package name or a local path, and it can…
A <Teleport> normally resolves its target the moment it mounts. If the target element does not exist yet, Vue logs a warning and renders nothing. This is a common problem when the target is rendered by the same component tree: a modal might teleport to a container that appears later in the template, or a…