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Let's prototype a JavaScript JIT compiler!

3 videos recommended on HN
YouTube
Cited on HN 4 times, 2023–2025, never outright recommended score 0
Years with an HN recommendation, 2007–2026

HN commenters cite it as a concrete example of how a skilled developer uses Copilot, mostly as fancy autocomplete for codebase-specific work.

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.

“He basically uses it as a fancy autocomplete.” (HN, 2025)

3 citations · 1 critical · Tutorials · advanced

4 Hacker News comments

From the HN archive; up to 20 kept per video, favoring different commenters. Recommendations first.

@Kiro Oct 2023 Cites it
on HN thread 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.
Example of Copilot helping with codebase-specific tasks.
@Kiro Nov 2023 Cites it
on HN thread 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.
Example of Copilot assisting tedious codebase-specific work.
@shakna Aug 2025 Cites it
on HN thread 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]
Shows Kling uses Copilot only as fancy autocomplete.
@Nullabillity Nov 2023 Pushes back
on HN thread 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!

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