Dirk
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ddv.tools
Dirk
@ddv.tools
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Backends & tooling. Working on a JS runtime, Maligator, for learning purposes.
GH: @dirkdev98
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ddv.tools
Builtin function calls landed in Maligator! Now supporting calling isFinite, isNaN, parseInt and parseFloat :)
Code snippet containing JS: const int = parseInt("5", 10) const finite = isFinite(int); finite; Shell executing Maligator: maligator [main][+241/-][ v24.12.0] ❯ node ./src/engine/tmp.ts { type: 'normal', value: EngineValue { type: 'boolean', data: { value: true } } }
January 11, 2026 at 7:03 PM
ddv.tools
With if-statements and (do-)while-loops supported in Maligator, it all starts to get some shape.
let x = 0; while (true) { if (x === 2) { break; } x++; } x; ❯ node ./src/engine/tmp.ts { type: 'normal', value: EngineValue { type: 'number', data: { value: 2 } } }
January 10, 2026 at 8:39 AM
ddv.tools
Chipped away at a few more things, so updating variables is supported as well. As well as some relational expressions. Next up are the if-, while-, etc-statements.
❯ node ./src/engine/tmp.ts 'let x = 1, y = 2; let xSmallerThenOne = 1 < 2; x++; x === y && xSmallerThenOne' { type: 'normal', value: EngineValue { type: 'boolean', data: { value: true } } }
January 8, 2026 at 7:19 AM
ddv.tools
Got basic variables going! Skipped the static semantics for now, which suggest to initialize all new variable bindings before executing a block.
Also an interesting thing in the spec is that `undefined` and a few others are properties on `global`. So only now can `undefined` actually be resolved.
❯ node ./src/engine/tmp.ts 'let x = 5, y = 5; { x + y; }' { type: 'normal', value: EngineValue { type: 'number', data: { value: 10 } } }
January 5, 2026 at 7:16 PM
ddv.tools
Figured it was time to get code running, so dove straight in to environment records, realms and execution context. For parsing, we just use Meriyah for now.
So with all that prep work, implementing binary expressions (1 + "foo") was really straight-forward.
Screenshot of terminal showing various executions of simple JS additions via the custom JS engine using 'node ./scr/engine/tmp.ts' [arg]'. Where arg is '"foo" + "bar"' or 'true + 1'
January 5, 2026 at 7:04 AM