If anyone wants to try out MicroQuickJS in a browser here's a simple playground interface for executing a WebAssembly compiled version of it: https://tools.simonwillison.net/microquickjs

It's a variant of my QuickJS playground here: https://tools.simonwillison.net/quickjs

The QuickJS page loads 2.28 MB (675 KB transferred). The MicroQuickJS one loads 303 KB (120 KB transferred).

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azakai 5 hours ago | parent | next [-]

Looks like those sizes could be improved significantly, as the builds include names etc. I would suggest linking with

emcc -O3

(and maybe even adding --closure 1 )

edit: actually the QuickJS playground looks already optimized - just the MicroQuickJS one could be improved.

	▲	simonw 4 hours ago \| parent [-]
		Nice. Got it down from 229KB to 148KB! Thanks for the tips. https://github.com/simonw/research/pull/5 Thats now live on https://tools.simonwillison.net/microquickjs

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kamranjon 3 hours ago | parent | prev | next [-]

I was interested to try Date.now() since this is mentioned as being the only part of the Date implementation that is supported but was surprised to find it always returns 0 for your microquickjs version - your quickjs variant appears to return the current unix time.

	▲	simonw an hour ago \| parent [-]
		Good catch. WebAssembly doesn't have access to the current time unless the JavaScript host provides it through injecting a function, so the WASM build would need to be hooked up specially to support that.

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throwaway290 2 hours ago | parent | prev [-]

The most important thing about any new JS runtime in 2025, how do I use it from JS? /s