Developer says they built a JavaScript runtime in one month — tiny, clever, and messy

What happened

It has been reported that a developer built "Ant," a tiny JavaScript runtime weighing in at about 2 MB, in roughly a month of spare-time hacking. The project is described in a personal blog post and allegedly includes full source, tests, and documentation on GitHub. Why bother? Because shipping a real JS engine without dragging hundreds of megabytes of V8 or Node sounds almost too good to be true — and that promise is what drove this sprint.

How it works

At the heart of the hack: NaN‑boxing. The author uses a typedef uint64_t jsval_t to pack every JavaScript value into a single 64‑bit word. Allegedly, numbers, objects, strings, functions and even promises are encoded in those bits by exploiting unused NaN payload space in IEEE‑754 doubles. A few compile‑time asserts protect the trick, and once it landed, many pieces suddenly ran faster and simpler. The dev iterated fast — days for variables, functions, loops; MDN became a feature checklist.

The garbage‑collection disaster

And then — the gut punch. Memory management. A JavaScript runtime needs GC, not manual frees, and implementing one turned into a weeks‑long nightmare. The blog reads like a survival story: manual free‑lists toggled on and off, integrations that wrecked performance, days where one fix broke three other things. This is the emotional core of the post: the quiet, soul‑draining work that separates a neat demo from something you can actually ship.

Why it matters

Tiny runtimes are an ongoing trend — lightweight embeddables, WASM ecosystems, and minimal tooling are all hungry for smaller, dependable engines. Ant is a sprint proof‑of‑concept that shows what's possible if you accept tradeoffs and ship fast. It has been reported that the code is available for others to poke at; will someone polish the GC, harden the parser, and turn this into a real alternative to the heavyweights? Time — and contributors — will tell.

Sources: themackabu.dev, Hacker News