tc39 proposals

tc39のproposals
throw expression
richer-keys
class-access-expression

1. tc39_study (throw_expressions) (Richer_Keys) (Class_Access_Expressions)
2. Name !CSO
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3. 5ISPX
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4. 8IBU
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5. function save(filename = throw new TypeError("Argument required")) { }
6. function getEncoder(encoding) { const encoder = encoding === "utf8" ? new UTF8Encoder() : encoding === "utf16le" ? new UTF16Encoder(f alse) : encoding === "utf16be" ? new UTF16Encoder(t rue) : throw new Error("Unsupported encoding"); }
7. *NQMFNFOUBUJPO ࣮͸ੲ7ʹ࣮૷͠·ͨ͠ɻ݁ہ$-͸"CBOEPO͠·͕ͨ͠ɻ
8. 1SPCMFN ࣮͸લఏͱͯ͠
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10. %PFYQSFTTJPO ͦͯ͠ߋʹEPFYQSFTTJPOͱ͍͏QSPQPTBM͕ࠓճఏҊ͞Ε͍ͯΔશͯͷ
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    ଟ෼TUBHF͕ਐΉ͜ͱ͸ͳ͍͔΋͠Εͳ͍ɻ
11. function save(filename = do { throw new TypeError("Argument required”) }) { } // σϑΥϧτύϥϝʔλͰͷdoࣜ͸·ͩະఆ
12. function getEncoder(encoding) { const encoder = encoding === "utf8" ? new UTF8Encoder() : encoding === "utf16le" ? new UTF16Encoder(f alse) : encoding === "utf16be" ? new UTF16Encoder(t rue) : do { throw new Error("Unsupported encoding”); } }
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15. $PMMFDUJPO\UP,FZ UP7BMVF^ $PMMFDUJPOʹUP,FZͱUP7BMVFΛ௥Ճ͢Δ
16. new Map([], { toKey(key) {return normalizedKey;}, toValue(value) {return normalizedValue;}, }); new WeakMap([], { toKey(key) {return normalizedKey;}, toValue(value) {return normalizedValue;}, }); new Set([], { toValue(value) {return normalizedValue;}, }); new WeakSet([], { toValue(value) {return normalizedValue;}, });
17. DPNQPTJUF,FZ
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18. compositeKey(...parts: [...any]) : Object.freeze({__proto__:null}) compositeSymbol(...parts: [...any]) : Symbol()
19. const myValues = new Map(); const components = [a, b]; const myKey = compositeKey(...components); myValues.set(myKey, components); // ... let [a, b] = myValues.get(myKey);
20. 4UBUVT UP,FZ͚ͩTUBHFʹͳΓ·ͨ͠ɻ
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21. $MBTT
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22. 8IBU
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23. class C { static f() { ... } g() { class.f(); } }
24. 1SPCMFNT
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25. %JTDVTT ࢀরํ๏͕૿͑Δͷ͸޷·͘͠ͳ͍
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26. 4UBUVT 4UBHF
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