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ヤバいESLint/TSLintルール作っちゃったかもしれない
boiyama
April 24, 2018
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ヤバいESLint/TSLintルール作っちゃったかもしれない
Roppongi.js #2 での発表資料です。
https://roppongi-js.connpass.com/event/82998/
boiyama
April 24, 2018
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Transcript
Ϡό ͍ E S L i n t / T
S L i n t ϧ ʔϧ ࡞ ͬ ͪ Ό ͬ ͨ ͔ ͠ Ε ͳ ͍ 2 0 1 8 . 4 . 2 4 R o p p o n g i . j s # 2
P ro f i l e • ϑϩϯτΤϯυΤϯδχΞ at PERSOL
• GitHub: boiyaa Twitter: boiyaaaaaa
Ͳ Μ ͳ ϧ ʔϧ ͔ return จΛېࢭͯ͠Έͨ eslint-plugin-no-return tslint-no-return
ݩʑଞͷؔܕݴޠνοΫͳจ๏Λਅࣅ͔ͨͬͨ ˍؔͷॻ͖ํΛἧ͔͑ͨͬͨతͳಈػɻ
// Error function foo(bar) { const baz = bar **
2; return baz; } // Error const foo = function (bar) { const baz = bar ** 2; return baz; }; // Error const foo = bar => { const baz = bar ** 2; return baz; }; // OK const foo = bar => bar ** 2;
Λฦؔ͢Λॻ࣌͘ʹɺΞϩʔؔͷ؆ܿจମ͔͠ ͑ͳ͘ͳΔ͚͔ͩͱࢥ͚ͬͨͲ จ͕ॻ͚ͳ͍؆ܿจମʹΑͬͯɺ৭ʑͳॻ͖ํΛ౷ҰͰ ͖ͨΓɺ Lint ϧʔϧΛγϯϓϧʹͰ͖ͨΓ͢Δ͜ͱʹؾ ͍ͮͨɻ
݅ͷॻ͖ํΛ౷ҰͰ͖ͯɺ ϧʔϧΛݮΒͤͨɻ
const foo = bar => { if (bar == "baz")
{ return "qux"; } return "quux"; }; const foo = bar => { switch (bar) { case "baz": { return "qux"; } default: { return "quux"; } } }; // ! const foo = bar => (bar == "baz" ? "qux" : "quux");
if switch ESLint ϧʔϧଟ͍ͷͰ͑ͳ͍ͳΒ͖ͬ͢ Γ͍͍ͯ͠ͱࢥ͏ɻ Ͱࡾ߲ԋࢉࢠ൱ఆ͕݁ߏ͍Δ͠ೖΕࢠϠό͍ɻ Ramda ΛͬͯΈΔͱ͔
const foo = bar => (bar == "baz" ? "qux"
: "quux"); // ! const foo = ifElse(equals("baz"), always("qux"), always("quux"));
const foo = (bar, baz) => { if (bar <
baz) { return "qux"; } else if (bar > baz) { return "quux"; } return "corge"; }; // ! const foo = cond([ [R.lt(R.__, R.__), R.always("qux")], [R.gt(R.__, R.__), R.always("quux")], [T, always("corge")] ]);
const foo = bar => { switch (bar) { case
"baz": { return "qux"; } case "quux": { return "corge"; } default: { return "grault"; } } }; // ! const foo = cond([ [equals("baz"), always("qux")], [equals("quux"), always("corge")], [T, always("grault")] ]);
ϧʔϓͷॻ͖ํΛ౷ҰͰ͖ͨɻ
const foo = bar => { const baz = [];
for (let i = 0; i < bar.length; i++) { baz.push(bar[i] ** 2); } return baz; }; // ! const foo = bar => bar.map(baz => baz ** 2);
const foo = count => { const baz = [];
for (let i = 0; i < count; i++) { baz.push(i ** 2); } return baz; }; // ! const foo = (count, baz, i) => i < count ? foo(count, [].concat(baz, [i ** 2]), i + 1) : baz;
for ͱ͔ while ͱ͔ॻ͚ͳ͍ͱɺྻ͍͍ͱͯ͠ɺ ؆ܿจମʴࡾ߲ԋࢉࢠͷ࠶ؼؔಡΈʹ͍͘ɻ ͜Ε Ramda Ͱॻ͍ͯΈΔɻ
const foo = bar => { const baz = [];
for (let i = 0; i < bar.length; i++) { baz.push(bar[i] ** 2); } return baz; }; // ! const foo = bar => bar.map(baz => baz ** 2); // ! const foo = bar => map(baz => baz ** 2, bar);
const foo = count => { const baz = [];
for (let i = 0; i < count; i++) { baz.push(i ** 2); } return baz; }; // ! const foo = (count, baz, i) => i < count ? foo(count, [].concat(baz, [i ** 2]), i + 1) : baz; // ! const foo = count => times(i => i ** 2, count);
มɾఆΛఆٛͰ͖ͳ͘ͳͬͨ
const foo = bar => { const baz = bar
** 2; return baz + baz; }; // ! const foo = bar => bar ** 2 + bar ** 2; // ! let ࣜ෩Ξϓϩʔν const foo = bar => (baz => baz + baz)(bar ** 2);
const foo = bar => { const baz = bar
** 2; const qux = baz ** 2; const quux = qux ** 2; return baz + qux + quux; }; // ! let ࣜ෩ΞϓϩʔνϠό͍ const foo = bar => (baz => ((baz, qux) => ((baz, qux, quux) => baz + qux + quux)(baz, qux, qux ** 2))( baz, baz ** 2 ))(bar ** 2);
// ͜ΜͳؔΛ࡞Δ const letin = (initialValue, funcs) => funcs .reduce(
(previousValue, func) => [ ...previousValue, func.apply(null, previousValue) ], initialValue ) .pop();
const foo = bar => { const baz = bar
** 2; const qux = baz ** 2; const quux = qux ** 2; return baz + qux + quux; }; // ! const foo = bar => letin( [bar], [ bar => bar * bar, (bar, baz) => baz * baz, (bar, baz, qux) => qux * qux, (bar, baz, qux, quux) => baz + qux + quux ] );
return Ҏ֎ͷจ͔͚ΔͷͰɺ Λฦ͞ͳ͍ؔͳΒͳΜͰ͋Γ
function foo(bar) { bar.baz = "qux"; bar.quux.push("corge"); } const foo
= function (callback) { callback(); }; const foo = () => { throw new Error("bar"); }; function* foo() { yield "bar"; }
· ͱ Ί • ESLint/TSLint ͷϧʔϧઃఆ͕γϯϓϧʹͳΔ • ͪΐͬͱίʔυॻ͖ʹ͍͘ • গͳ͍ϧʔϧͰ৭ʑͳॻ͖ํ੍͕ݶ͞ΕΔ͜ͱࣗମ
͍͍͔ͳͱࢥ͍ͬͯΔ
Έ͍ͨͳ