投稿時間:2022-07-31 04:21:02 RSSフィード2022-07-31 04:00 分まとめ(22件)

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js	JavaScriptタグが付けられた新着投稿 - Qiita	Firebase(v9) から取得したIDトークンをサーバサイド(Node.js)で検証する	https://qiita.com/kamekame85/items/ad328741cdbde49615ae	namespac	2022-07-31 03:34:50
海外TECH	DEV Community	Statements in Programming	https://dev.to/graciousdev/statements-in-programming-3m33	Statements in ProgrammingWhat are Statements A statement is the smallest unit in an imperative programming language It is formed by a sequence of one or more statement A statement will have internal components called expression A definition is different from a statement in that a statement contains executable code while definitions declare an identifier Types of Statements Simple Statements•assignment A A •call CLEARSCREEN •return return •goto goto •assertion assert ptr NULL Compound Statements•block•if statement•switch statement•while loop•do loop•for loop Assignments StatementsAn assignment statement sets the value or changes the value stored in the storage locations denoted by a variable name Thank you for reading this article	2022-07-30 18:42:22
海外TECH	DEV Community	Programming and Properties of Programming Languages	https://dev.to/graciousdev/programming-and-properties-of-programming-languages-3kkd	Programming and Properties of Programming LanguagesWhat is Programming This is the process of writing testing debugging and maintenance of the source code of computer programs It s purpose is to create a program which will set instructions which that the computer uses to perform specific functions to to exhibit desired behaviors Properties of Programming Languages ReliabilityA Programming Language in order to be classified as a Programming Language has to be reliable A fundamental calculation must be give the sameness answer all the time RobustnessA Programming Language must be robust it must be able to execute instructions without collapsing UsabilityA Programming Language must be usable Programmers must Ben able to use it for whatever purpose it is meant for without being overly difficult to use PortabilityPortability is another great Properties of a Programming Language A Programming Language must have an engine which does not take up all the resources of the computer only to execute few instructions MaintainabilityThe Programming Language must be designed in such a way that is maintainable It should be relatively easy to debug Thank you for reading this article	2022-07-30 18:31:26
海外TECH	DEV Community	useEffect firing twice in React 18	https://dev.to/shivamjjha/useeffect-firing-twice-in-react-18-16cg	useEffect firing twice in React GistAcoording to React Changelog In the future React will provide a feature that lets components preserve state between unmounts To prepare for it React introduces a new development only check to Strict Mode React will automatically unmount and remount every component whenever a component mounts for the first time restoring the previous state on the second mount If this breaks your app consider removing Strict Mode until you can fix the components to be resilient to remounting with the existing state So in short When Strict Mode is on React mounts components twice in development only to check and let you know it has bugs This is in development only and has no effect in code running in production If you just came here to know why your effects are being called twice that s it that s the gist You can spare reading this whole article and go fix your effectsHowever you can stay here and know some of the nuances But first what is an effect According to beta react docs Some components need to synchronize with external systems For example you might want to control a non React component based on the React state set up a server connection or send an analytics log when a component appears on the screen Effects let you run some code after rendering so that you can synchronize your component with some system outside of React The after rendering part here is quite important Therefore you should keep this in mind before adding an effect to your component For example you might be setting some state in an effect based on a local state or a prop change function UserInfo firstName lastName const fullName setFullName useState Avoid redundant state and unnecessary Effect useEffect gt setFullName firstName lastName firstName lastName return lt div gt Full name of user fullName lt div gt Just don t Not only it is unnecessary but it will cause an unnecessary second re render when the value could ve been calculated during renderfunction UserInfo firstName lastName Good calculated during initial render const fullName firstName lastName return lt div gt Full name of user fullName lt div gt But what if calculating some value during a render is not as cheap as our fullName variable here Well in that case you can memoize an expensive calculation You still don t have any need to use an Effect herefunction SomeExpensiveComponent const data useMemo gt Does no re run unless deps changes return someExpensiveCalculaion deps deps This tells React to not re calculate data unless deps changes You only need to do this even when someExpensiveCalculaion is quite slow say takes ms to run But it s up to you First see is it fast enough without a useMemo then build up from there You can check the time it takes to run a piece of code using console time or performance now console time myBadFunc myBadFunc console timeEnd myBadFunc You can see log like myBadFunc ms or so You can now decide whether to use useMemo or not Also even before using React memo you should first read this awesome article by Dan Abramov What is useEffectuseEffect is a react hook that lets you to run side effects in your components As discussed previously effects run after a render and are caused by rendering itself rather than by a particular event An event can be a user icon for example clicking a button Hence useEffect should be only used for synchronization since it is not just fire and forget The useEffect body is reactive in the sense whenever any dependencies in the dependency array change the effect is re fired This is done so that the result of running that effect is always consistent and synchronized But as seen this is not desirable It can be very tempting to use an effect here and there For example you want to filter a list of items based on a specific condition like cost less than ₹ You might think to write an effect for it to update a variable whenever the list of items changes function MyNoobComponent items const filteredItems setFilteredItems useState Don t use effect for setting derived state useEffect gt setFilteredItems items filter item gt item price lt items As discussed it is inefficient React will be needing to re run your effects after updating state amp calculating and updating UI Since this time we are updating a state filteredItems React needs to restart all of this process from step To avoid all this unnecessary calculation just calculate the filtered list during render function MyNoobComponent items Good calculating values during render const filteredItems items filter item gt item price lt So rule of thumb When something can be calculated from the existing props or state don t put it in state Instead calculate it during rendering This makes your code faster you avoid the extra “cascading updates simpler you remove some code and less error prone you avoid bugs caused by different state variables getting out of sync with each other If this approach feels new to you Thinking in React has some guidance on what should go into the state Also you don t need an effect to handle events For example a user clicking a button Let s say you want to print a user s receipt function PrintScreen billDetails Don t use effect for event handlers useEffect gt if billDetails myPrettyPrintFunc billDetails billDetails I am guilty of writing this type of code in past Just don t do it Instead in the parent component where you might be setting billDetails as setBillDetails on a user s click of button just do yourself a favor and print it there only function ParentComponent return Good useing inside event hanler lt button onClick gt myPrettyPrintFunc componentState billDetails gt Print Receipt lt button gt The code above is now free of bugs caused by using useEffect in the wrong place Suppose your application remembers the user state on page loads Suppose user closes the tab because of some reason and comes back only to see a print pop up on the screen That s not a good user experience Whenever you are thinking about whether code should be in an event handler or in useEffect think about why this code needs to be run Was this because of something displayed to screen or some action event performed by the user If it is latter just put it in an event handler In our example above the print was supposed to happen because the user clicked on a button not because of a screen transition or something shown to the user Fetching DataOne of the most used use cases of effects in fetching data It is used all over the place as a replacement for componentDidMount Just pass an empty array to array of dependencies and that s all useEffect gt Don t fetching data in useEffect without a cleanup const f async gt setLoading true try const res await getPetsList setPetList res data catch e console error e finally setLoading false f We have all seen and probably written this type of code before Well what s the issue First of all useEffects are client side only That means they don t run on a server So the initial page rendered will only contain a shell of HTML with maybe a spinnerThis code is prone to errors For example if the user comes back clicks on the back button and then again re opens the page It is very much possible that the request that the first fired before the second one may get resolved after So the data in our state variable will be stale Here in the code above it may not be a huge problem but it is in the case of constantly changing data or for eample querying data based on a search param while typing in input it is So fetching data in effects leads to race conditions You may not see it in development or even in production but rest assured that many of your users will surely experience this useEffect does not take care of caching background updates stale data etc which are necessary in apps that are not hobby This requires a lot of boilerplate to write by hand and hence is not easy to manage and sustain Well does that mean any fetching should not happen in an effect no function ProductPage useEffect gt This logic should be run in an effect because it runs when page is displayed sendAnalytics page window location href event feedback form useEffect gt This logic is related to when an event is fired hence should be placed in an event handler not in an effect if productDataToBuy proceedCheckout productDataToBuy productDataToBuy The analytics request made is okay to be kept in useEffect since it will fire when the page is displayed In Strict Mode in development in React useEffect will fire twice but that is fine See here how to deal with that In many projects you can see effects as a way of syncing queries to user inputs function Results query const res setRes useState null Fetching without cleaning up useEffect gt fetch results endpoint query query then setRes query Maybe this seems opposite to what we discussed previously to put fetching logic in an event handler However here the query may come from any source user input url etc So the results need to be synced with the query variable However consider the case we discussed before that the user may press the back button and then forward button then the data in res state variable may be stale or consider the query coming from user input and user typing fast The query might change from p to po to pot to pota to potat to potato This might initiate different fetches for each of those values but it is not guaranteed that they will come back in that order So the results displayed may be wrong of any of the previous queries Hence cleanup is required here which ensures that results shown are not stale and prevents race conditions function Results query const res setRes useState null Fetching with cleaning up useEffect gt let done false fetch results endpoint query query then data gt if done setRes data return gt done true query This makes sure that only the latest response from all responses is accepted Just handling race conditions with effects might seem like a lot of work However there is much more to data fetching such as caching deduping handling state data background fetches etc Your framework might provide an efficient in built data fetching mechanisms than using useEffect If you don t want to use a framework you can extract all the above logic to a custom hook or might use a library like TanStack Query previously known as useQuery or swr So FaruseEffect fires twice in development in Strict Mode to point out that there will be bugs in production useEffect should be used when a component needs to synchronize with some external system since effects don t fire during rendering process and hence opt out of React s paradigm Don t use an effect for event handlers Don t use effect for derived state Heck don t even use the derived state as long as possible and calculate values during render Don t use effect for data fetching If you are in a condition where you absolutely cannot avoid this at least cleanup at the end of the effect Credits Much of the content above is shamelessly inspired from Beta React DocsDan Abramov s tweetsLiked it Checkout my blog or Read this post on my blog	2022-07-30 18:22:00
海外科学	NYT > Science	Debris From Uncontrolled Chinese Rocket Falls Over Southeast Asian Seas	https://www.nytimes.com/2022/07/30/science/china-rocket-debris-fall.html	Debris From Uncontrolled Chinese Rocket Falls Over Southeast Asian SeasTo launch part of its space station to orbit China used a large rocket that cannot control its atmospheric re entry It is the third time such a rocket has been used	2022-07-30 18:50:39
ニュース	BBC News - Home	Community Shield: Liverpool 3-1 Man City - Darwin Nunez seals victory	https://www.bbc.co.uk/sport/football/62275194?at_medium=RSS&at_campaign=KARANGA	shield	2022-07-30 18:19:30
ニュース	BBC News - Home	Euro 2022: England captain says final 'start of journey' for equality in society	https://www.bbc.co.uk/sport/football/62364228?at_medium=RSS&at_campaign=KARANGA	Euro England captain says final x start of journey x for equality in societyEngland captain Leah Williamson says the Euro final against Germany on Sunday is the not the end but the start of a journey	2022-07-30 18:17:37
ニュース	BBC News - Home	Commonwealth Games: Scotland's Jack Carlin wins keirin silver	https://www.bbc.co.uk/sport/commonwealth-games/62364288?at_medium=RSS&at_campaign=KARANGA	commonwealth	2022-07-30 18:22:13
ニュース	BBC News - Home	Community Shield highlights: Darwin Nunez stars as Liverpool beat Man City	https://www.bbc.co.uk/sport/av/football/62365475?at_medium=RSS&at_campaign=KARANGA	Community Shield highlights Darwin Nunez stars as Liverpool beat Man CityDarwin Nunez comes off the bench to star for Liverpool as they beat Manchester City in the Community Shield at Leicester s King Power Stadium	2022-07-30 18:48:11
ニュース	BBC News - Home	Commonwealth Games 2022: Ben Proud wins England's first swimming gold	https://www.bbc.co.uk/sport/av/commonwealth-games/62365069?at_medium=RSS&at_campaign=KARANGA	birmingham	2022-07-30 18:48:34
ニュース	BBC News - Home	Watch: Sportscene - Scottish Premiership highlights	https://www.bbc.co.uk/sport/av/football/62320179?at_medium=RSS&at_campaign=KARANGA	sportscene	2022-07-30 18:31:05
ビジネス	ダイヤモンド・オンライン - 新着記事	【精神科医からのアドバイス】職場で古い考えの人と理解しあえず、溝が深まり自分が退職しました。どうすれば歩み寄れるようになるでしょうか？ - 生きづらいがラクになる ゆるメンタル練習帳	https://diamond.jp/articles/-/306639		2022-07-31 03:55:00
ビジネス	ダイヤモンド・オンライン - 新着記事	【ベストセラー精神科医が発表！】 メンタルダウンの人がついやってしまう習慣【ワースト3】 - 真の「安定」を手に入れるシン・サラリーマン	https://diamond.jp/articles/-/305329		2022-07-31 03:50:00
ビジネス	ダイヤモンド・オンライン - 新着記事	優秀な人たちとの競争を避けて成果を出す「別解」がやめられない理由 - 起業家の思考法	https://diamond.jp/articles/-/305486	問題解決	2022-07-31 03:45:00
ビジネス	ダイヤモンド・オンライン - 新着記事	【マンガ】東大グローバルフェローが教える「企業の情報開示」を数理的に研究した超興味深い論文とは？ - １６歳からのはじめてのゲーム理論	https://diamond.jp/articles/-/307232		2022-07-31 03:40:00
ビジネス	ダイヤモンド・オンライン - 新着記事	【出口学長・日本人が最も苦手とする哲学と宗教講義】 そもそもシーア派は どうして生まれたのか？ - 哲学と宗教全史	https://diamond.jp/articles/-/305542		2022-07-31 03:35:00
ビジネス	ダイヤモンド・オンライン - 新着記事	「決断できない人」に欠けている1つのこと - 幸せな自信の育て方	https://diamond.jp/articles/-/306844		2022-07-31 03:30:00
ビジネス	ダイヤモンド・オンライン - 新着記事	【現役サラリーマンが株式投資で2.5億円】 毎月3万～6万円のコツコツ積立投資で 20～30年後、これだけの金額に増える - 割安成長株で2億円 実践テクニック100	https://diamond.jp/articles/-/306672	【現役サラリーマンが株式投資で億円】毎月万万円のコツコツ積立投資で年後、これだけの金額に増える割安成長株で億円実践テクニック仕事がつらすぎて定年まで働くなんて無理……そうだ、生涯賃金億円を株式投資で稼いでしまおう そう決意した入社年目、知識ゼロの状態から株式投資を始めた『割安成長株で億円実践テクニック』の著者・現役サラリーマン投資家の弐億貯男氏。	2022-07-31 03:25:00
ビジネス	ダイヤモンド・オンライン - 新着記事	「気づきにくい投資の大チャンス」を見逃さない方法 - 東大金融研究会のお金超講義	https://diamond.jp/articles/-/307296	「気づきにくい投資の大チャンス」を見逃さない方法東大金融研究会のお金超講義年月に発足した東大金融研究会。	2022-07-31 03:20:00
ビジネス	ダイヤモンド・オンライン - 新着記事	【暗殺の世界史】英雄カエサルの「暗殺」でローマに起こったパニックとは？ - アメリカの中学生が学んでいる14歳からの世界史	https://diamond.jp/articles/-/307259	【暗殺の世界史】英雄カエサルの「暗殺」でローマに起こったパニックとはアメリカの中学生が学んでいる歳からの世界史発売直後から大きな話題を呼び、中国・ドイツ・韓国・ブラジル・ロシア・ベトナム・ロシアなど世界各国にも広がった「学び直し本」の圧倒的ロングセラーシリーズ「BigFatNotebook」の日本版が刊行。	2022-07-31 03:15:00
ビジネス	ダイヤモンド・オンライン - 新着記事	【9割の人が知らないGoogleの使い方】 高コスパ・高セキュリティ・生産性劇的向上！今、ZoomからGoogle Meetに乗り換えるべき3大メリットとは - Google 式10Xリモート仕事術	https://diamond.jp/articles/-/306915	【割の人が知らないGoogleの使い方】高コスパ・高セキュリティ・生産性劇的向上今、ZoomからGoogleMeetに乗り換えるべき大メリットとはGoogle式Xリモート仕事術神田昌典氏絶賛刷Google認定トレーナーがあなたの生産性劇的アップを神サポート「リモート弱者」が「リモート強者」変わる神メソッドITビギナーから絶大な信頼を得ている平塚氏は、Googleが授与する資格Google認定トレーナーGoogleCloudPartnerSpecializationEducationをつ保有する国内唯一の女性トレーナー経営者。	2022-07-31 03:10:00
ビジネス	ダイヤモンド・オンライン - 新着記事	【本日は7月最終LUCKYデー】 2枚同時に見るだけで、突然、とんでもない運気降臨！ 銀座×祇園＝2大風水パワーのダブル強運貯金の新・開運法 - 1日1分見るだけで願いが叶う！ふくふく開運絵馬	https://diamond.jp/articles/-/306131	【本日は月最終LUCKYデー】枚同時に見るだけで、突然、とんでもない運気降臨銀座×祇園大風水パワーのダブル強運貯金の新・開運法日分見るだけで願いが叶うふくふく開運絵馬フジテレビ「FNNLiveNewsイット」で話題沸騰見るだけで「癒された」「ホッとした」「本当にいいことが起こった」と話題沸騰刷Amazon・楽天位。	2022-07-31 03:05:00