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
With support for for-loops, `new String()` and various new prototype methods, our Test262 number just went up to 4166.
February 16, 2026 at 7:02 AM
ddv.tools
Some more progress on Maligator, a JS runtime in TypeScript, in the last two weeks:

- Switch-statements
- try-catch-finally
- Array and object literals
- Function, Error, TypeError
- And more intrinsic methods for things like Function#bind, Array#map, Object.create, etc.
- A Test262 runner 🤓
February 8, 2026 at 9:37 PM
ddv.tools
Slowly starting to take a look at Test262. Just the basic harness, Test262Error and assert, need a few more language features than we support currently. So added support for `new`, `this` and `throw`. Try-catch-finally is up next!
January 25, 2026 at 9:05 PM
ddv.tools
Some more has gone in to Maligator, my JS runtime implemented in TypeScript.
I've started with the real basic intrinsics and finally a way to create JS objects. Combine that with member expressions and we have `[object Object]`.
Local.js code snippet ``` // function fibonacciRecursive(n) { // if (n < 2) { // return n; // } // return fibonacciRecursive(n - 1) + fibonacciRecursive(n - 2); // } // // fibonacciRecursive(11); let x = Object(null); x.foo = Object(null); x.foo.toString(); ``` Result from running that via Maligator `EngineValue { type: 'string', data: { value: '[object Object]' } }`
January 18, 2026 at 2:19 PM
ddv.tools
And with a final push of adding TODO's everywhere, we got function declarations and calling working 🤓
Execution of local.js via Maligator: ``` function add(a, b) { return a + b; } add(1, 2); ``` With result: ``` EngineValue { type: 'number', data: { value: 3 } } ```
January 12, 2026 at 9:21 PM
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
Over the holidays I have started to work on a JavaScript engine. Mainly to get more experience w/ specification driven interpreter development, learning some new intricacies of JS and having a big project where lots of parts can be implemented without much thinking
January 5, 2026 at 7:04 AM