Rock-Solid JavaScript through Applied Science

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www.karakun.com Rock-solid JavaScript through Applied Science Prof. Dierk König

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2 Dierk König Fellow at Karakun Prof at FHNW @mittie @ProfDKoenig https://dierk.github.io/Home

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3 Oxymoron JavaScript and Rock-solid JavaScript and Applied Science

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4 Computability Turing Machine Lambda Calculus Recursive Functions

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-BNCEB$BMDVMVT ЋBMQIB3FOBNF1BSBNFUFS 3FGBDUPSJOH ЌCFUB"QQMZ"SHVNFOU БFUB$BODFM1BSBNFUFS

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"MQIB5SBOTMBUJPO DPOTUJEYY DPOTUJEZZ

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#FUB3FEVDUJPO GYG Y JE YJE Y JE YY

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&UB3FEVDUJPO YZQMVT Y Z YQMVT Y QMVT

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"UPNJD-BNCEB5FSNT // atoms const id = x => x; const fst = x => y => x; const snd = x => y => y;

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1BJS // atoms const id = x => x; const fst = x => y => x; const snd = x => y => y; const Pair = x => y => accessor => accessor(x)(y);

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1BJS$SFBUJPO // atoms const id = x => x; const fst = x => y => x; const snd = x => y => y; const Pair = x => y => accessor => accessor(x)(y); const point = Pair(1024)(200);

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1BJS"DDFTT // atoms const id = x => x; const fst = x => y => x; const snd = x => y => y; const Pair = x => y => accessor => accessor(x)(y); const point = Pair(1024)(200); point(fst); // 1024, compare to pair.fst point(snd); // 200, compare to pair.snd the basic product type

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5SJQMF $BOZPVFODPEFUSJQMFTCZGPMMPXJOH UIFTBNFQBUUFSOBTGPSQBJST /5VQMFT

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5VQMFT6TBHF const [Person, firstname, lastname, age] = Tuple(3); const dierk = Person('Dierk')('König')(51); dierk(firstname); // 'Dierk', compare to dierk.firstname

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1BJS 5VQMF FUD /PUFUIBUPVSQBUUFSOMFBETUP immutableWBMVFT PCKFDUT "DDFTTPSGVODUJPOTBSFlazyVOUJM UIFZBSFBQQMJFE CFUBSFEVDFE

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&JUIFS $P1SPEVDU 4VN const Left = x => f => g => f(x); // ctor 1 const Right = x => f => g => g(x); // ctor 2 const either = e => f => g => e(f)(g); // accessor const safeDiv = x => y => y === 0 ? Left ("divisor is zero") : Right(x / y); either ( safeDiv(1)(0) ) ( msg => console.log(msg) ) ( res => id(res) ) η-reduce

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3FGBDUPSJOH"MHFCSB const Left = x => f => g => f(x); // ctor 1 const Right = x => f => g => g(x); // ctor 2 const either = e => f => g => e(f)(g); // accessor const safeDiv = x => y => y === 0 ? Left ("divisor is zero") : Right(x / y); either ( safeDiv(1)(0) ) ( console.log ) ( id ) η-reduce

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3FGBDUPSJOH"MHFCSB const Left = x => f => g => f(x); // ctor 1 const Right = x => f => g => g(x); // ctor 2 const either = e => f => e(f) ; // accessor const safeDiv = x => y => y === 0 ? Left ("divisor is zero") : Right(x / y); either ( safeDiv(1)(0) ) ( console.log ) ( id ) η-reduce

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&JUIFS $P1SPEVDU 4VN const Left = x => f => g => f(x); // ctor 1 const Right = x => f => g => g(x); // ctor 2 const either = e => e ; // accessor const safeDiv = x => y => y === 0 ? Left ("divisor is zero") : Right(x / y); either ( safeDiv(1)(0) ) ( console.log ) ( id ) definition

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&JUIFS $P1SPEVDU 4VN const Left = x => f => g => f(x); // ctor 1 const Right = x => f => g => g(x); // ctor 2 const either = id ; // accessor const safeDiv = x => y => y === 0 ? Left ("divisor is zero") : Right(x / y); either ( safeDiv(1)(0) ) ( console.log ) ( id )

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&JUIFS .BZCF FUD /PUFUIBUPVSQBUUFSOMFBETUP null-safeDPNQVUBUJPO :PVcannot forgetUPDPWFSBMM DBTFT FHUIFOVMMPSFSSPSDBTF

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$IPJDF $BOZPVFODPEFNVMUJQMFDIPJDFTCZ GPMMPXJOHUIFTBNFQBUUFSOBTGPS &JUIFS

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3FBM8PSMEVTBHF8FC4IPQ1BZNFOU0QUJPOT const [Cash, CreditCard, Transfer, match] = Choice(3); // generalized sum type const pay = payment => match(payment) ( () => amount => 'pay ' + amount + ' cash') ( ( { number, sec } ) => amount => 'pay ' + amount + ' with credit card ' + number + ' / ' + sec) ( ( [ from, to ] ) => amount => 'pay ' + amount + ' by wire from ' + from + ' to ' + to); let payment = Cash(); assert.is( pay(payment)(50), 'pay 50 cash'); payment = CreditCard( { number: '0000 1111 2222 3333', sec: '123' } ); assert.is( pay(payment)(50), 'pay 50 with credit card 0000 1111 2222 3333 / 123'); payment = Transfer(['Account 1', 'Account 2']); assert.is( pay(payment)(50), 'pay 50 by wire from Account 1 to Account 2');

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24 Rock-solid Science Rock-solid immutable "Objects" Null-safe operations that cover all cases All done with lambda expressions

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25 Repository https://github.com/Dierk/ BrushUpYourJavaScript

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26 Credits Gabriel Lebec @g_lebec Daniel Dietrich @danieldietrich

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27 Further Support Engineering, Consulting, Training Certificate of Advanced Studies

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