投稿時間:2021-09-07 07:15:07 RSSフィード2021-09-07 07:00 分まとめ(17件)

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TECH	Engadget Japanese	KDDI、新サービス発表会を9月13日に開催	https://japanese.engadget.com/kddi-event-215257344.html	新サービス	2021-09-06 21:52:57
Google	カグア！Google Analytics 活用塾:事例や使い方	バランスチェアおすすめ6選は体型と身長に合わせて選ぶといいよー。10年近くバランスチェア使ってるけど実はいろいろな姿勢で座ってる。	https://www.kagua.biz/review/interior/20210907b1.html	長時間	2021-09-06 21:00:44
js	JavaScriptタグが付けられた新着投稿 - Qiita	Node.js: docxをhtmlにするMammoth	https://qiita.com/e99h2121/items/9b307907a41256032232	after	2021-09-07 06:06:24
Program	[全てのタグ]の新着質問一覧｜teratail（テラテイル）	PILがinstallしてもIDLE Shellで使えません。	https://teratail.com/questions/358106?rss=all	PILがinstallしてもIDLEShellで使えません。	2021-09-07 06:27:02
AWS	AWSタグが付けられた新着投稿 - Qiita	AWS CLIからDynamoDBを操作してみる。	https://qiita.com/Ooooooomin_365/items/0d61c916aa8dee745abd	データの挿入awsdynamodbputitemtablenametestdynamoDbitemTestKeySTestKeyitemSテストちゃんと値が入ったことが確認できました同じキーを持つ項目がすでにテーブル内にある場合はその値が上書きされます。	2021-09-07 06:24:58
海外TECH	DEV Community	Master objects in JS 🍨 (Part 2)	https://dev.to/jrmatanda/master-objects-in-js-part-2-2fnn	Master objects in JS Part Objects and PrototypesLike many object oriented languages JavaScript provides support for implementation inheritance the reuse of code or data through a dynamic delegation mechanism But unlike many conventional languages JavaScript s inheritance mechanism is based on prototypes rather than classes For many programmers JavaScript is the first object oriented language they encounter without classes In many languages every object is an instance of an associated class which provides code shared between all its instances JavaScript by contrast has no built in notion of classes Instead objects inherit from other objects Every object is associated with some other object known as its prototype Working with prototypes can be different from classes although many concepts from traditional object oriented languages still carry over Understand the difference between prototype getPrototypeOf and proto Prototypes involve three separate but related accessors all of which are named with some variation on the word prototype This unfortunate overlap naturally leads to quite a bit of confusion Let s get straight to the point C prototype is used to establish the prototype of objects created by new C Object getPrototypeOf obj is the standard ES mechanism for retrieving obj s prototype object obj proto is a nonstandard mechanism for retrieving obj s prototype objectTo understand each of these consider a typical definition of a JavaScript datatype The User constructor expects to be called with the new operator and takes a name and the hash of a password string andstores them on its created object function User name passwordHash this name name this passwordHash passwordHash User prototype toString function return User this name User prototype checkPassword function password return hash password this passwordHash let u new User sfalken efaeecbdcb The User function comes with a default prototype property containing an object that starts out more or less empty In this example we add two methods to the User prototype object toString and checkPassword When we create an instance of User with the new operator the resultant object u gets the object stored at User prototypeautomatically assigned as its prototype object The image below shows a diagram of these objectsNotice the arrow linking the instance object u to the prototype objectUser prototype This link describes the inheritance relationship Property lookups start by searching the object s own properties for example u name and u passwordHash return the current values of immediate properties of u Properties not found directly on u are looked up in u s prototype Accessing u checkPassword for example retrieves a method stored in User prototype This leads us to the next item in our list Whereas the prototype property of a constructor function is used to set up the prototype relationship of new instances the ES function Object getPrototypeOf canbe used to retrieve the prototype of an existing object So for example after we create the object u in the example above we can test Object getPrototypeOf u User prototype trueThis illustrates the prototype relationships for the User constructor andinstance Some environments produce a nonstandard mechanism for retrievingthe prototype of an object via a special proto property This canbe useful as a stopgap for environments that do not support ES s Object getPrototypeOf In such environments we can similarly test u proto User prototype trueA final note about prototype relationships JavaScript programmers will often describe User as a class even though it consists of little more than a function Classes in JavaScript are essentially the combination of a constructor function User and a prototype object used to share methods between instances of the class User prototype This is a conceptual view of the User “class The image above provides a good way to think about the User class conceptually The User function provides a public constructor for the class and User prototype is an internal implementation of the methods shared between instances Ordinary uses of User and u have no need to access the prototype object directly Things to Remember C prototype determines the prototype of objects created by new C Object getPrototypeOf obj is the standard ES function for retrieving the prototype of an object obj proto is a nonstandard mechanism for retrieving the prototype of an object A class is a design pattern consisting of a constructor function andan associated prototype Prefer Object getPrototypeOf to proto ES introduced Object getPrototypeOf as the standard API for retrieving an object s prototype but only after a number of JavaScript engines had long provided the special proto property for the same purpose Not all JavaScript environments support this extension however and those that do are not entirely compatible Environments differ for example on the treatment of objects with a null prototype In some environments proto is inherited from Object prototype so an object with a null prototype has no special proto property var empty Object create null object with no prototype proto in empty false in some environments In others proto is always handled specially regardless of an object s state var empty Object create null object with no prototype proto in empty true in some environmentsWherever Object getPrototypeOf is available it is the more standard and portable approach to extracting prototypes Moreover the proto property leads to a number of bugs due to its pollution ofall objects JavaScript engines that currently support the extension may choose in the future to allow programs to disable it in order to avoid these bugs Preferring Object getPrototypeOf ensures that code will continue to work even if proto is disabled For JavaScript environments that do not provide the ES API it is easy to implement in terms of proto if typeof Object getPrototypeOf undefined Object getPrototypeOf function obj var t typeof obj if obj t object amp amp t function throw new TypeError not an object return obj proto This implementation is safe to include in ES environments because it avoids installing the function if Object getPrototypeOf already exists Things to Remember Prefer the standards compliant Object getPrototypeOf to the non standard proto property Implement Object getPrototypeOf in non ES environments thatsupport proto Never modify proto The special proto property provides an additional power that Object getPrototypeOf does not the ability to modify an object s prototype link While this power may seem innocuous after all it s just another property right it actually has serious implications and should be avoided The most obvious reason to avoid modifying proto is portability Since not all platforms support the ability tochange an object s prototype you simply can t write portable code that does it Another reason to avoid modifying proto is performance All modern JavaScript engines heavily optimize the act of getting and setting object properties since these are some of the most common operations that JavaScript programs perform These optimizations are built on the engine s knowledge of the structure of an object When you change the object s internal structure say by adding or removing properties to the object or an object in its prototype chain some of these optimizations are invalidated Modifying proto actually changes the inheritance structure itself which is the most destructive change possible This can invalidate many more optimizations than modifications to ordinary properties But the biggest reason to avoid modifying proto is for maintaining predictable behavior An object s prototype chain defines its behavior by determining its set of properties and property values Modifying an object s prototype link is like giving it a brain transplant It swaps the object s entire inheritance hierarchy It may be possible to imagine exceptional situations where such an operation could be helpful but as a matter of basic sanity an inheritance hierarchy should remain stable For creating new objects with a custom prototype link you can use ES s Object create For environments that do not implement ES Item provides a portable implementation of Object create that does not rely on proto Things to Remember Never modify an object s proto property Use Object create to provide a custom prototype for new objects Thank you for reading the second part this article Don t forget to checkout the third part of this serie Make your Constructors new Agnostic And if you want more in depth knowledge about your favorite programming languages checkout my personal blog to become an on demand developer and you can find me on twitter as well	2021-09-06 21:23:10
海外TECH	DEV Community	Video preview on hover with HTML and JavaScript	https://dev.to/juanbelieni/video-preview-on-hover-with-html-and-javascript-1b00	Video preview on hover with HTML and JavaScriptIn this post I will be showing how to add a preview feature for the videos inside your HTML page First I will be using this simple HTML code as the base to create the preview feature lt video gt lt source src gt lt video gt So to start we should create the startPreview and stopPreview functions To contextualize the preview will be played during seconds starting after the first second at a playback rate of The startPreview will set the values so that the preview will be played as mentioned and stopPreview will reset the values to the default ones const video document querySelector video function startPreview video muted true video currentTime video playbackRate video play function stopPreview video currentTime video playbackRate video pause After it we should create the event listeners so that the preview can be played on hover To accomplish this a timeout will be used to stop the preview after seconds let previewTimeout null video addEventListener mouseenter gt startPreview previewTimeout setTimeout stopPreview video addEventListener mouseleave gt clearTimeout previewTimeout previewTimeout null stopPreview It s important to clear the timeout every time the user leaves the video area because it can happen that a previous timeout stops the video when the user enters the video area for a second time before the seconds Here is the result	2021-09-06 21:13:24
Apple	AppleInsider - Frontpage News	Apple says achieved pay equity, urges employees to report workplace issues to management	https://appleinsider.com/articles/21/09/06/apple-says-achieved-pay-equity-urges-employees-to-report-workplace-issues-to-management?utm_medium=rss	Apple says achieved pay equity urges employees to report workplace issues to managementApple SVP of retail and people Deirdre O Brien in an internal video to employees last week addressed pay equity and workplace issues both topics that are the source of growing discontent among company staff O Brien told workers that she knows a few employees have raised concerns over pay equity but claimed Apple has achieved equilibrium across gender and race according to The Verge reporter Zoe Schiffer who shared details of the statement in a post to Twitter on Friday The executive added that Apple s approach to the issue is best in class In early August Apple squashed internal discussion of pay equity by shutting down three separate employee run surveys The company cited inclusion of personally identifiable information and ownership of the systems used to host the surveys as justification for the takedown Read more	2021-09-06 21:42:52
ニュース	BBC News - Home	The Wire star Michael K Williams found dead	https://www.bbc.co.uk/news/world-us-canada-58470253?at_medium=RSS&at_campaign=KARANGA	media	2021-09-06 21:54:27
ニュース	BBC News - Home	US Open 2021: Emma Raducanu into quarter-finals after beating Shelby Rogers	https://www.bbc.co.uk/sport/tennis/58469496?at_medium=RSS&at_campaign=KARANGA	US Open Emma Raducanu into quarter finals after beating Shelby RogersBritish teenager Emma Raducanu puts in another devastating performance to reach the US Open quarter finals as her dream New York debut continues	2021-09-06 21:17:15
ニュース	BBC News - Home	UK fires up coal power plant as gas prices soar	https://www.bbc.co.uk/news/business-58469238?at_medium=RSS&at_campaign=KARANGA	natural	2021-09-06 21:03:40
ニュース	BBC News - Home	Solheim Cup 2021: Matilda Castren claims winning point as Europe retain the trophy	https://www.bbc.co.uk/sport/golf/58470233?at_medium=RSS&at_campaign=KARANGA	castren	2021-09-06 21:53:41
ニュース	BBC News - Home	Man Utd to start Covid spot-checks on matchdays	https://www.bbc.co.uk/sport/football/58469827?at_medium=RSS&at_campaign=KARANGA	newcastle	2021-09-06 21:03:13
北海道	北海道新聞	筒香は４打数２安打２打点	https://www.hokkaido-np.co.jp/article/586458/	筒香	2021-09-07 06:12:58
北海道	北海道新聞	責任能力ありと判断へ、水戸地検　家族４人殺傷事件の容疑者	https://www.hokkaido-np.co.jp/article/586459/	殺傷事件	2021-09-07 06:02:00
ビジネス	東洋経済オンライン	JR西｢普通列車で荷物輸送｣実施までの全舞台裏 毎週木曜日､伯備線で岡山駅に野菜を運ぶ | 経営 | 東洋経済オンライン	https://toyokeizai.net/articles/-/449882?utm_source=rss&utm_medium=http&utm_campaign=link_back	普通列車	2021-09-07 06:30:00
ニュース	Newsweek	初心者が知らない、勝ち続ける投資家が必ず守る「ルール」	https://www.newsweekjapan.jp/stories/carrier/2021/09/post-97052.php	つまり、年後までの成長を織り込んで現在の株価を評価するなら、PER倍であっても決して高すぎるということにはなりません。	2021-09-07 06:30:00