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Learning about [Symbol.toPrimitive] while writing tests for Object.groupBy(). I had no idea that this was introduced with #ES6 already.
Somehow it feels that writing nice useful objects with #JavaScript's standard library is quite feasible.
I am preparing for #ctwebdev ... cu in Cologne?
![it('the [Symbol.toPrimitive] is the new `toString` (since ES6)', () => {
const obj = {};
obj[Symbol.toPrimitive] = () => 'from toPrimitive';
assert.equal(obj.toString(), '[object Object]');
// BUT
assert.equal(String(obj), 'from toPrimitive');
assert.equal('' + obj, 'from toPrimitive');
});](https://media.mastodontech.de/media_attachments/files/113/470/098/775/417/804/original/9c5523123052e0d9.png)
I could spend an eternity just digging into the depth of #JavaScript the Language and its specification. There is always new stuff to discover and it is all so well structured and very teaching when exploring it with tests.
Join me on Thursday at #ctwebdev on "JavaScript the Language: Diving Deep in a Test-Driven Way" – what a long and clunky title.
See also https://jslang.dev for more #JavaScript learnings.
#jslang
@jensgro Yep, Slides sind erreichbar unter [object Object].
@wolframkriesing
DAS ist auch klasse.
DAS solltest Du bringen 
DAs ist doch für Dich und den @sir_pepe ein prima Pulli oder T-Shirt:
https://webbed-briefs.teemill.com/product/undefined-oversized/
@jensgro @wolframkriesing von da hab ich schon EINIGE! Wähle das Motiv jeweils passend zur Konferenz 
@jensgro @sir_pepe
danke, den schenk ich mir zu Weihnachten :)
das hier ist auch geil https://webbed-briefs.teemill.com/product/javascript-is-a-puzzle/
@wolframkriesing Viel Erfolg!