Track Element Visibility Using Intersection Observer
A look into how we can use the Intersection Observer API in JavaScript to efficiently track element visibility and how it outperforms historical alternatives.
Articles
JavaScript, page 6 of 18
JavaScript is probably one of the most‑used programming languages in the world, and a cornerstone of front‑end (and more general) web development. It enables the development of interactivity and features that HTML and CSS alone simply cannot, and includes more advanced concepts like closures, callbacks, and asynchronous programming.
Below you will find a subset of articles from my blog specifically about JavaScript. This is an area I have worked with for many years, and it has been a regular subject in my writing. There are three hundred nineteen articles collected together for you below.
Track Element Visibility Using Intersection Observer. 
Deep‑Cloning vs. Shallow‑Cloning in JavaScript. Deep‑Cloning vs. Shallow‑Cloning in JavaScript
Not all object copies in JavaScript behave the same way. Explore the difference between deep‑cloning and shallow‑cloning, when to use each, and common pitfalls.
Component Apis Before React Hooks Settled. Component Apis Before React Hooks Settled
A retrospective on React component APIs before hooks settled, covering render props, higher‑order components, context, classes, and migration judgement.
Mastering JavaScript Iterators and Generators. Mastering JavaScript Iterators and Generators
A practical guide to JavaScript iterators and generators, with lazy sequences, custom iteration, generator control flow, and the trade‑offs behind both.
Access Search Parameters in Next.js SSR'd Layout. Access Search Parameters in Next.js SSR'd Layout
Whilst replatforming an app, I came across this limitation in Next.js: you cannot (easily) access search parameters in an SSR layout. Here, I share my solution.
Flattening Arrays in JavaScript. Flattening Arrays in JavaScript
Flatten arrays in JavaScript with flat(), recursion, stacks, depth control, compatibility notes, and performance trade‑offs for nested data safely.
Unit Testing in Angular: Writing Effective Tests. Unit Testing in Angular: Writing Effective Tests
How to write effective Angular unit tests that focus on behaviour, TestBed boundaries, realistic setup, and assertions that survive refactoring over time.
Use JavaScript to Find the Week Day from a Date. Use JavaScript to Find the Week Day from a Date
Find the weekday from a JavaScript date with Date, UTC alternatives, modulo arithmetic, parsing caveats, daylight saving time, and readable day names.
Understanding Object Types with JavaScript's instanceof. Understanding Object Types with JavaScript's
instanceofUncover the differences between JavaScript's `instanceof` and `typeof` for type checking, with practical examples and insights on when to use each operator.
Implementing Authentication in Next.js Using NextAuth.js. Implementing Authentication in Next.js Using NextAuth.js
A practical guide to implementing authentication in Next.js with NextAuth.js, including sessions, callbacks, route protection, and router‑specific trade‑offs.
Reduce() in JavaScript. reduce()in JavaScriptUnderstand JavaScript reduce() with accumulator patterns, initial values, practical examples, readability trade‑offs, and when reduce() genuinely helps.
Creating Progressive Web Apps (PWAs) with Angular. Creating Progressive Web Apps (PWAs) with Angular
How to build a Progressive Web App with Angular, including service workers, caching, offline behaviour, installs, and the trade‑offs behind the defaults.
Object Equality in JavaScript: {} isn't Equal to {}. Object Equality in JavaScript:
{}isn't Equal to{}In JavaScript two empty objects are not equal. One of my go‑to interviewing questions, here I offer an explanation and strategies to compare object contents.
Pure Functions in JavaScript. Pure Functions in JavaScript
Pure functions make JavaScript easier to test, reason about, and reuse. This guide explains what purity means and why it matters in everyday code.
Understanding the Composition API in Vue 3. Understanding the Composition API in Vue 3
The Vue 3 Composition API explained with practical TypeScript examples, refs, composables, reactivity, and when the pattern genuinely helps larger components.
Angular Change Detection: How It Works and How to Optimise It. Angular Change Detection: How It Works and How to Optimise It
Angular change detection explained through zone triggers, OnPush, signals, template cost, manual checks, and practical rendering optimisation at scale.
How View Source Stopped Being Enough. How View Source Stopped Being Enough
Why view source stopped being enough for modern web checks, and how rendered HTML, hydration, metadata, schema, crawl paths, and client output changed audits.
Validating Parentheses Input Using TypeScript. Validating Parentheses Input Using TypeScript
Validate parentheses input in TypeScript with a stack, checking bracket order, matching pairs, real parser‑style use cases, and alternative approaches.