web — the showcases in the browser

Source on GitHub ↗

Three little browser apps, each powered by rakupp compiled to WebAssembly — the same interpreter as the CLI, running entirely client-side. No server and no JavaScript re-implementation: each app builds a Raku program (a showcase's own code plus your input) and shows what it prints.

App	What it does
`markdown.html`	live Markdown editor — type on the left, see it rendered on the right
`json.html`	JSON beautifier / minifier
`regex.html`	Raku regex tester with live match highlighting + a grammar parse-tree explorer

Run them

No server. Generate the embedded assets once, then just open the HTML files:

showcase/web/bundle.sh
# then open showcase/web/index.html  (double-click, or `open showcase/web/index.html`)

bundle.sh builds Raku.js if needed (rakujs/build.sh), then writes lib/: the Emscripten loader, the WebAssembly binary as base64 (lib/rakujs-wasm.js), and the two CLI showcase sources the JSON/Markdown apps reuse (lib/sources.js). The pages load those with plain <script src> and run the interpreter on the page — so they work opened straight from disk, file://, no http server at all.

lib/ is git-ignored; re-run bundle.sh to refresh it after rebuilding Raku.js.

Don't want to build anything? Each tagged release attaches rakujs-showcase-web-<tag>.zip — these apps with the WebAssembly already embedded. Download, unzip, open index.html. No toolchain, no server.

How it works

runner.js is a tiny main-thread Raku client: raku.run(src) returns a Promise<{out, err, rc, ms}>, plus a debounced() helper for live editing and a rakuHeredoc() that embeds arbitrary user text as a non-interpolating Raku heredoc. It instantiates the interpreter by handing Emscripten the embedded wasm as a data: URL (locateFile), so nothing is fetched over the network.
Each app reuses the relevant showcase from lib/sources.js (e.g. the md2html source), strips its file-reading MAIN, appends a driver that binds your input and calls the showcase's function (render, to-json, …), runs it, and renders the result — on every keystroke, debounced. (regex.html builds its program inline, so it needs no source.)

So the app is thin; the actual Markdown/JSON/grammar work is the very same Raku code the CLI showcases run.

Running on the main thread (rather than a Web Worker like the playground) keeps this simple and file://-openable; the trade-off is no Stop button and a brief freeze on heavy input — fine for these keystroke-fast apps.

Notes / gotchas

Output must end in a newline. WebAssembly stdout is line-buffered — a final line printed with print (no \n) is held until the next run. The apps use say so every result flushes immediately.
No sockets, no filesystem. The sandbox can't run the server showcases (pastebin, rakus, chat, kvstore) — those need real TCP.
Recursion is capped at a few hundred levels (a WebAssembly stack limit, not a Raku one); deeply recursive programs that run fine natively can hit it here.
These are browser apps, so they aren't part of the t/run.raku suite; the Raku code they exercise is covered there via the CLI showcases.