Let's prototype a JavaScript JIT compiler!
Why Hacker News recommends it
HN commenters cite it as a concrete example of how a skilled developer uses Copilot, mostly as fancy autocomplete for codebase-specific work.
What it is
Andreas Kling live-codes a prototype JavaScript JIT compiler for the LibJS engine used in SerenityOS and Ladybird. He builds a standalone bytecode VM, a simple interpreter, and then a simple JIT in about 80 minutes.
Recommended by 0 HN commenters across 0 different months, 2023 to 2025.
What Hacker News said
Cites Kiro · 2023-10 · on “Stack Overflow announces 28% headcount reduction”
The stuff Copilot helps me with is not the stuff SO could help me with. Check out 6:05 and 6:25 in this Andreas Kling video: [this video] That's where Copilot shines, not for locating and copypasting answers from Stack Overflow.
Cites Kiro · 2023-11 · on “Krita AI Diffusion”
> The code is usually the same code I'd get a few web searches away My impression is that people normally don't use Copilot as a substitute for finding solutions (ChatGPT is much better for that), but as a way to help with otherwise tedious tasks that are really specific to your codebase. Check out 6:05 and 6:25 in this Andreas Kling video for a good example: [this video] Regarding your second point Copilot helps me when I least expects it. I think the video illustrates what I mean with that as well.
Cites shakna · 2025-08 · on “This Month in Ladybird”
Ladybird is 425k LOC. Chromium is 3.5m LOC. Starting a new browser, using LLMs... Is not going to maintain enough context. Whilst Andreas does use Copilot a fair bit [0], he tends to do a line at a time, frequently disagree and rewrites his own, before prompting again. That is... He basically uses it as a fancy autocomplete. Not much else. [0] [this video]
Critical Nullabillity · 2023-11 · on “Krita AI Diffusion”
> Check out 6:05 and 6:25 in this Andreas Kling video for a good example: [this video] Oof. So not only was it a poor replacement for a macro, it didn't even generate the correct code!