tc39 x jsconf.jp Panel Discussion

2023/09/25 @ Recruit South Tower
TC39 x JSConf.jp Collaboration Event

Transcript

1. TC39 x JSConf.jp
   
   
   Panel Discussion
   2023/09/25 @ South Tower Tokyo
   

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2. We will talk about JS
   weakpoints, next features,
   and so on.
   

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3. First, take a look at our
   survey.
   

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4. Excited proposals
   

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5. Which proposal are you
   most excited? / Ͳͷϓϩϙ
   ʔβϧʹظ଴Λ͍ͯ͠·͢
   ͔ʁ
   

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6. Most exciting proposals
   • Temporal x 12
   
   
   • Pipeline operator x 10
   
   
   • Pattern Matching x 7
   
   
   • Record and Tuple x 5
   
   
   • JSON Modules x 3
   

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7. Temporal
   // Stage 3
   const zonedDateTime = Temporal.ZonedDateTime.from({
   timeZone: 'America/Los_Angeles',
   year: 1995,
   month: 12,
   day: 7,
   hour: 3,
   minute: 24,
   second: 30,
   millisecond: 0,
   microsecond: 3,
   nanosecond: 500
   }); // => 1995-12-07T03:24:30.0000035-08:00[America/Los_Angeles]
   

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8. Pipeline operator
   // Stage 2
   // Previous
   const json = await npmFetch.json(npa(pkgs[0]).escapedName, opts);
   // With pipes
   const json = pkgs[0]
   |> npa(%).escapedName
   |> await npmFetch.json(%, opts);
   

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9. Pattern Matching
   // Stage 1
   match (res) {
   when ({ status: 200, body, ...rest }): handleData(body, rest)
   when ({ status, destination: url }) if (300 <= status && status <
   400):
   handleRedirect(url)
   when ({ status: 500 }) if (!this.hasRetried): do {
   retry(req);
   this.hasRetried = true;
   }
   default: throwSomething();
   }
   

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10. Record and Tuple
    // Stage 2
    const record = #{ prop: 1 };
    const tuple = #[1, 2, 3];
    Record.isRecord(record); // true
    Record.isRecord({ prop: 1 }); // false
    // Equality
    #{ a: 1 } === #{ a:1 } // true
    #[1] === #[1] // true
    

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11. JSON Modules
    // Stage 3
    import foo from "foo.json" with { type: "json" };
    

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12. Which proposals are
    exciting? (TC39 team?)
    • Iterator helpers
    
    
    • Pattern matching, modules declarations, deferred
    imports, compartments
    
    
    • temporal
    
    
    • Array.fromAsync
    
    
    • type annotation
    

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13. Weak points
    

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14. Do you have current
    JavaScript weak points?
    and what are the weak
    points? / ͲΜͳ఺͕
    JavaScriptͷऑ఺ͩͱࢥ͍·
    ͔͢ʁ
    

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15. JavaScript weak points
    • ݹ͍ػೳͱͷޓ׵ੑΛ࣋ͨͳ͍ͱ͍͚ͳ͍఺ɻ
    
    
    • JS needs to have an interoperability for legacy features.
    
    
    • This is not weak, strong point.
    
    
    • JS survives 20 years.
    
    
    • Backword compats are really important.
    
    
    • Some aspects of JS make it harder, such as being able to modify
    prototypes
    
    
    • To keep compatibility is needed. documentation is also important.
    

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16. JavaScript weak points
    • Some parts are scattered in various specs (e.g. ECMA262 does not
    have Cancellation. It's relying on DOM AbortController)
    
    
    • ECMA262 ͚ͩ͡Όͳͯ͘ɺଞͷ࢓༷΋ݟ͓͔ͯͳ͍ͱ͍͚ͳ͍ͱ͜Ζ
    ʢྫ͑͹ɺΩϟϯηϧ͸DOM AbortController ͱ͔ݟͯͳ͍ͱ͍͚ͳ
    ͍ʣ
    
    
    • Cancellation is misunderstandable... it is not ECMA262 spec.
    
    
    • JS is just the language, it is not runtime environment. some other
    langs have similar architecture.
    
    
    •
    

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17. JavaScript weak points
    • ESM and CJS separate the JS world.
    
    
    • ESMͱCommonJSͰ΍͸Γੈք͕෼அ͞Εͯ
    ͠·͏ॴ
    
    
    •
    

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18. JavaScript weak points
    • Immutability is weaker than other langs
    
    
    • ෆมΛఏڙ͢Δػೳ͕ଞͷݴޠʹൺ΂ͯऑ͍ࣄ
    
    
    • Most js objects are mutable, so it is hard.
    
    
    • Object.freeze / seal are pragmatic...
    
    
    • Haskell is ever thing is immutable, python, c++, Java are
    not so immutable. It depends on design?
    
    
    • TS is not so immutable either.
    

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19. JavaScript weak points
    • ະఆٛϝϯόΞΫηε΁ݫີͳ੍ޚ͕Ͱ͖ͣ
    unde
    fi
    ned ͕ޙͰൃ֮͢Δ఺ɻ
    
    
    • JS developers could not handle unde
    fi
    ned
    property access and
    fi
    nd these faults at production.
    
    
    • TypeScript will help you!!
    
    
    • Optional chaining ?. will help you!!
    

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20. JavaScript weak points
    • Coercing Things
    
    
    • (NaN Λ 0 ͱͯ͠ѻͬͨΓ string ౉͞ͳ͖Ό͍͚
    ͳ͍ͱ͜Ζʹ number ౉ͨ͠Βউखʹcastͨ͠Γ)
    
    
    • New APIs should not handle these unpredictable
    behaviour
    
    
    • Throw errors if the types are invalid.
    

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21. JavaScript weak points
    • Prototype Pollution
    
    
    • ϓϩτλΠϓԚછͳΜͱ͔ͳΒΜʁ
    
    
    • 1. locked down (built-in prototype is frozen, global object is
    also freezed)
    
    
    • 2. realm proposal (create new environment / realm,
    prototype polluted in the environment, but it is not affected
    all world. shadow realms are stage3, )
    
    
    • node vm module does not solve security problems.
    

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22. Discussion:
    
    
    (Yosuke's talk)
    

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23. ESM status
    • TypeScript con
    fi
    g `module` props have many options like es2022,
    nodenext, bundler, etc.
    
    
    • this prop nightmare is introduced by Node.js CJS / ESM options.
    
    
    • Node.js has CJS / ESM interop feature.
    
    
    • Historically, CJS is needed in Node.js.
    
    
    • ESM was declared in 2015.
    
    
    • Node.js core committer thought 2 specs would cause migration issues.
    
    
    • So, Node.js implemented CJS / ESM interops using the
    fi
    le extension
    and the package.json `type`
    fi
    eld.
    

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24. ESM status
    • Spec difference:
    
    
    • ESM and CJS are totally different.
    
    
    • ESM: async load / CJS: sync load
    
    
    • ESM: static / CJS: dynamic
    
    
    • ESM: pass by reference / CJS: pass by value
    

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25. ESM status
    • My opinion:
    
    
    • TypeScript developers feel Node.js brings ESM/CJS
    nightmare.
    
    
    • Node.js developers feel if CJS/ESM interop has never
    been implemented, migration nightmare will start.
    
    
    • I guess TC39 people think module system is required
    and it would be better to be browser friendly (CJS is
    not ideal it is for Node.js / Server-side).
    

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26. 😇 My Opinion:
    
    
    This is nobody's fault.
    
    
    Future prediction is hard.
    

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