Articles
Beyond the lessons
Long-form pieces on the JavaScript questions working developers actually search for — written in the same voice as the course, each one linking back to the lessons it builds on.
Alert Document.Cookie: What It Shows and HidesSee what alert(document.cookie) reveals, why cookies go missing, how to read one safely, and what HttpOnly changes.
Image Slider in JavaScript: Accessible and ResponsiveBuild a responsive JavaScript image slider with accessible controls, keyboard navigation, swipe gestures, lazy loading, and reduced motion.
Sorting Arrays in JavaScript: A Practical GuideChoose sort() or toSorted(), then build reliable comparators for numbers, dates, strings, missing values, and multi-key object sorting.
Why Uint8Array Negative Assignments Wrap to 255Uint8Array converts negative and oversized values with truncation and mathematical modulo 256, so assigning -1 stores 255.
Sizeof Array in JavaScript: Length vs. BytesUse array.length for slots, byteLength for typed arrays, and TextEncoder for serialized UTF-8 bytes. Heap memory needs a profiler.
Array Size in JavaScript: A Visual GuideUse array.length for the index range, then choose a different count for occupied slots or matching values.
JavaScript Switch Statement: A Visual GuideSee how JavaScript switch matching, fall-through, case scope, useful patterns, and safer alternatives work.
Submit Events and composed: false in Shadow DOMWhy native submit events stay inside a shadow root, when they reach document, and three correct form component patterns.
JavaScript [object Object]: Meaning and FixesLearn why JavaScript prints [object Object], trace coercion, inspect values correctly, and handle JSON.stringify failures.
Optional Chaining an Undeclared VariableWhy undeclaredVar?.prop throws ReferenceError, when optional chaining returns undefined, and which guard fixes each cause.
How to Count in JavaScriptCount array items, matching values, frequencies, Unicode text, DOM elements, function calls, and page state with the right JavaScript pattern.
FormData JavaScript: Forms, Files, and FetchBuild FormData from forms, preserve repeated fields and files, send it with fetch, and diagnose missing entries or broken boundaries.
Tutoriales de Node.js: De Cero a una API ProbadaInstala Node.js 24 LTS y crea una API JSON con ESM, async/await, archivos, variables de entorno y pruebas integradas.
ECMAScript Await Continuations and Promise JobsHow await stores a promise reaction, suspends an async function, and resumes it through a browser microtask.
Radio Buttons in JavaScript: A Complete GuideBuild, read, select, validate, and submit radio buttons with null-safe JavaScript, FormData, and event delegation.
How to Extend Error in JavaScriptExtend Error with a reusable class that preserves causes, supports stable codes, serializes safely, and works with instanceof.
JavaScript Counter: Build One Step by StepBuild a JavaScript counter with shared state, limits, accessible controls, rendering, and validated localStorage persistence.
JavaScript forEach Loop: A Visual GuideSee how JavaScript forEach visits array elements, passes callback arguments, handles mutations, and behaves with async code.
JavaScript Sleep: How to Pause Without BlockingCreate a non-blocking JavaScript sleep, cancel it in the browser, use Node.js timers, and choose the right alternative.
How To Navigate In JavaScriptChoose between links, location, History API, and the newer Navigation API for full-page and single-page JavaScript navigation.
JavaScript Projects for Practice: 18 Ideas With Specs18 JavaScript practice projects in three tiers, each with the concept it forces, acceptance criteria to build against, and the specific trap it hides.
JavaScript Classes: How They Actually WorkHow class fields, private elements and inheritance actually run, in order, and what survives JSON.stringify, structuredClone and instanceof.
Key-Value Pairs in JavaScript: Objects vs MapsEvery object key becomes a string, Map keys do not. The coercion rule, the key order rule, the enumeration matrix, and when to reach for each store.
How to Prompt for Yes or No in JavaScriptconfirm() gives you a yes/no answer in one line, but its buttons say OK and Cancel. Here is why, and how to build a real Yes/No dialog you can await.
Node.js Tutorial: From Install to a Running ServerInstall the right Node line, settle CommonJS vs ESM, learn the six event loop phases, and serve JSON with no dependencies.
JS Printing: Console Output vs. Printing a PageJavaScript has two unrelated kinds of printing: console output, and window.print() sending the document to paper. Here is how each one actually works.
Java vs JavaScript: The Real Differences, ExplainedJava and JavaScript are unrelated languages that share a name from a 1995 deal. What actually differs: types, numbers, objects, equality, threads.
JavaScript void 0: What It Means and When to Use Itvoid is an operator that always returns undefined; javascript:void(0) is a link that goes nowhere. What each half does, and what to use instead.
Delegation in JavaScript: Events, Prototypes, PitfallsOne listener on a container can handle clicks from every row inside it. The matching rule that survives nested markup, the events that cannot be delegated, the four ways delegation fails silently, and the other thing the word means.