JavaScript

Node.js 27.0.0-alpha.0.1.0 (Alpha)

Reading a golf swing from a 9-axis IMU on a TV box: the calibration notes that actually mattered

A small sensor strapped near the shaft, a TV box rendering the shot, and a player who expects the ball to go where they aimed. Six months of that taught us that the hard part is never the fusion math — it is agreeing on…

Free gold price and exchange rate API: no key, JSON

Crystal Ball Markets publishes three free JSON files: exchange rates against the US dollar for 60 currencies, the gold price in local money for 69 countries, and live quotes for 212 markets. There is no key and no…

Roman Numerals Are a Subtractive Notation: Parsing Them Backwards Is a Bug Factory

Roman Numerals Are a Subtractive Notation: Parsing Them Backwards Is a Bug Factory Roman numerals look like a simple lookup table. They are not — they are a positional system with a subtractive rule, and almost every…

Solving for the Rate: Why r = n((A/P)^(1/(nt)) - 1) Breaks in Real Code

Solving for the Rate: Why r = n((A/P)^(1/(nt)) - 1) Breaks in Real Code You rarely need to quote an interest rate. You need to back one out of a number you already have: an advertised APY, a loan's effective cost, a…

Loan Payment Math: The Fixed-Payment Formula and the Five Bugs Around It

Loan Payment Math: The Fixed-Payment Formula and the Five Bugs Around It The fixed-payment loan formula is one of the most reproduced snippets on the internet, and most copies are subtly wrong in the same three places:…

I Built a Cheapest Fuel Station Map from Spanish Open Data

Spain publishes the price of every public fuel station as open data. The feed is refreshed every 30 minutes, contains roughly 11,500 stations and needs no API key. That sounded like a good small project: download the…

Writing a forex position size calculator in JavaScript: the pip value bugs

Most forex position size calculators online are one formula: lots = risk / (stop_pips × pip_value) That formula is right. The bugs live in the two inputs nobody explains: the pip value, and what you do with the number…

Free OpenAI-compatible LLM APIs in 2026: how to switch `base_url` in Python and JS

Free OpenAI-compatible LLM APIs in 2026: how to switch base_url in Python and JS You do not need a new SDK for every free LLM API. If a provider documents an OpenAI-compatible endpoint, the official Python and…

I built a tool that films websites being built, commit by commit

I wanted coding videos that people who don't code could enjoy too. Most "speed coding" videos are a sped-up screen recording: lots of scrolling, a terminal, then a website appears at the end. Non-developers have no idea…

Сколько стоит сайт в 2026 году: честные цифры от веб-студии

Каждый месяц к нам в студию приходят с одним и тем же вопросом: «Сколько стоит сайт?» Самый частый ответ — «зависит от задач», и никого он не устраивает. Поэтому решили честно: вот реальные диапазоны цен на 2026 год и…

How to connect with MERN stack developers community? can anyone help me ?

QR codes for print: the module math behind "make it bigger"

"The QR code doesn't scan" is almost never a bug in the generator. It's usually a print size problem, and print size is simple math once you know what a QR code is made of. Here's the math, with numbers from the qrcode…

Why I Built 14 Privacy-First Browser Tools Using WebAssembly & WebGPU (No Uploads, Free Forever)

Most online utility websites work the same way: you upload a confidential PDF, photo, or audio file to a random server, wait in a queue, dodge popups, and hit a paywall when you try to download the result. I got tired…

Building a Concurrency-Safe WhatsApp & Google Sheets Pipeline with Real-Time Error Alerts

When teachers across 50+ batches finish classes at the top of the hour, dozens of attendance messages hit your webhook simultaneously. If your backend is Google Apps Script writing to Google Sheets, simultaneous writes…

Building a JSON Formatter That Never Sees Your Data

Paste an API response into most formatters and it travels to a server first. Mine formats it in your browser — here is the 20 lines of JavaScript that do it. Every developer has done it: copy a minified API response,…

The element you cannot find is inside a blob iframe, and querySelector will never see it

Three hours of a recent debugging session went into a single wrong assumption: that the editor I was automating lived in the same document as the page I had loaded. document.querySelectorAll('[contenteditable]')…

Google Ads showed a 192% conversion rate. Here is the GA4 tracking bug behind it, and a script that catches it

Last month I opened a Google Ads account and saw something that should be impossible: one Search campaign reporting a 192.63% conversion rate. Almost two conversions for every click. It was not a great month. It was a…

I made i18next up to 5x faster with two includes() checks

Two includes() checks made i18next up to 5x faster on long text. This post shows that fix and two more. A regular expression is a good tool, but it is not free. Each call scans the input, and a bad pattern can scan the…

What the Sentry SDK drops after a 429 quota response

I'm building an error tracker, and I needed to know what an official Sentry SDK does when my ingest answers "you're over quota". I couldn't find anyone showing the wire, so I put a stub server in front of @sentry/node…