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tc39 proposals
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Taketoshi Aono(青野健利 a.k.a brn)
October 09, 2019
Programming
0
840
tc39 proposals
tc39のproposals
throw expression
richer-keys
class-access-expression
Taketoshi Aono(青野健利 a.k.a brn)
October 09, 2019
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Transcript
tc39_study (throw_expressions) (Richer_Keys) (Class_Access_Expressions)
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About IUUQJOGPCODI
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8IBUJTUISPXFYQSFTTJPO 5ISPXΛFYQSFTTJPO͔͠ॻ͚ͳ͍ॴͰॻ͚ΔΑ͏ʹͨ͠
function save(filename = throw new TypeError("Argument required")) { }
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"); }
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1SPCMFN ͨͩ͠ɺ&DNBTDSJQUʹ͓͚ΔTUBUFNFOUͱFYQSFTTJPOͷࠞಉ͕ ݴޠΛΑΓෳࡶʹͯ͠͠·͏ͷͰਐలͳ͘ UISPXFYQSFTTJPOʹؔͯ͠จ๏ͷՃʹରͯ͠ωΨςΟϒͳ͕݁ग़ͯ ͍ͯTUBHFʹਐΉ͜ͱͳͦ͞͏
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function save(filename = do { throw new TypeError("Argument required”) })
{ } // σϑΥϧτύϥϝʔλͰͷdoࣜ·ͩະఆ
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”); } }
1SPQPTBMSJDIFSLFZT
$PNQPTFEQSPQPTBM $PMMFDUJPO\UP,FZ UP7BMVF^ͱDPNQPTJUF,FZ DPNQPTJUF4ZNCPM ͷ̎ͭͷQSPQPTBMͷΈ߹Θͤ ͲͪΒΦϒδΣΫτͷࣝผʹ͍ͭͯ
$PMMFDUJPO\UP,FZ UP7BMVF^ $PMMFDUJPOʹUP,FZͱUP7BMVFΛՃ͢Δ
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;}, });
DPNQPTJUF,FZ DPNQPTJUF4ZNCPM ෳͷΦϒδΣΫτ͔ΒΩʔΛੜ͢Δ DPNQPTJUF,FZͱDPNQPTJUF4ZNCPM"1*ΛՃ͢Δ Ҿͷॱং͕ҧ͚Εҧ͏ΩʔͱͳΔ Ωʔʹར༻͞ΕͨΦϒδΣΫτ8FBL.BQͰཧ͞ΕΔͷͰΦϒδΣΫτ ͕ফ͑ΕϝϞϦ͔Βফ͑Δ
compositeKey(...parts: [...any]) : Object.freeze({__proto__:null}) compositeSymbol(...parts: [...any]) : Symbol()
const myValues = new Map(); const components = [a, b];
const myKey = compositeKey(...components); myValues.set(myKey, components); // ... let [a, b] = myValues.get(myKey);
4UBUVT UP,FZ͚ͩTUBHFʹͳΓ·ͨ͠ɻ UP7BMVF͕ඞཁ͔Ͳ͏͔͕TUBHFͰͷٞʹͳΓͦ͏
$MBTTBDDFTTFYQSFTTJPO
8IBUJTUIJT ΫϥεΦϒδΣΫτΞΫηε͢ΔҰ؏ͨ͠ํ๏Λఆٛ͢Δ
class C { static f() { ... } g() {
class.f(); } }
1SPCMFNTTPGBS TUBUJDͳΫϥεؔͷதͰUIJTΛͬͨ߹ɺؔͷݺͼग़͞ΕํʹΑͬͯ UIJT͕มΘΔ Ϋϥε໊Λͬͯ'PPCBSͱͨ͠߹ɺ'PPΛԿॻ͘ͷ%3:ʹͯ͠ ͍Δ UIJTDPOTUSVDUPS͔ΒࢀরͰ͖Δ͕ɺಉ͘͡UIJT͕TBGFͰͳ͍
%JTDVTT ࢀরํ๏͕૿͑Δͷ·͘͠ͳ͍ 'PPCBSͷΑ͏ʹΫϥε໊ͰΞΫηε͢Δͷ͕γϯϓϧͰΑ͍ %3:Λߟ͑ΔͱUIJTDPOTUSVDUPS͕ͩɺ҆શͰͳ͍ DMBTTCBSͰ͍͍͔͠Εͳ͍
4UBUVT 4UBHFʹͳΓ·ͨ͠