8,037 Matching Annotations
- Dec 2022
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blog.engelke.com blog.engelke.com
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dexie.org dexie.org
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```js import React from "react"; import Dexie from "dexie"; import { useLiveQuery } from "dexie-react-hooks"; import { db } from "./db";
// // React component // export function OldFriendsList() { const friends = useLiveQuery( () => db.friends .where('age') .above(75) .toArray() );
if (!friends) return null; // Still loading.
return
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{ friends.map(friend =>
- {friend.name}, {friend.age} ) }
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bugs.webkit.org bugs.webkit.org
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codepen.io codepen.io
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www.boxcryptor.com www.boxcryptor.com
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www.w3.org www.w3.org
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event.paris.fr event.paris.fr
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blog.engelke.com blog.engelke.com
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blog.engelke.com blog.engelke.com
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pomcor.com pomcor.com
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stackoverflow.com stackoverflow.com
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samnewman.io samnewman.io
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philcalcado.com philcalcado.com
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github.com github.com
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cheatsheetseries.owasp.org cheatsheetseries.owasp.org
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cheatsheetseries.owasp.org cheatsheetseries.owasp.org
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developer.mozilla.org developer.mozilla.org
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Modern browsers will reset Window.name to an empty string if a tab loads a page from a different domain, and restore the name if the original page is reloaded (e.g. by selecting the "back" button).
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www.thomasfrank.se www.thomasfrank.se
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blog.ropnop.com blog.ropnop.com
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developer.chrome.com developer.chrome.com
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wicg.github.io wicg.github.io
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www.crypto101.io www.crypto101.io
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datatracker.ietf.org datatracker.ietf.org
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datatracker.ietf.org datatracker.ietf.org
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jibbering.com jibbering.com
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stackoverflow.com stackoverflow.com
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security.stackexchange.com security.stackexchange.com
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javascript.info javascript.infoClosure1
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developer.mozilla.org developer.mozilla.orgClosures1
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itnext.io itnext.io
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gist.github.com gist.github.com
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stackoverflow.com stackoverflow.com
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javascript.plainenglish.io javascript.plainenglish.io
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bradyjoslin.com bradyjoslin.com
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coolaj86.com coolaj86.com
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noiseprotocol.org noiseprotocol.org
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stackoverflow.com stackoverflow.com
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Generate the keys using WebCrypto and mark them as non exportable Store the key into IndexedDB
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voracious.dev voracious.dev
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mdn.github.io mdn.github.io
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w3c.github.io w3c.github.io
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blog.cloudflare.com blog.cloudflare.com
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www.christian-faure.net www.christian-faure.net
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www.w3.org www.w3.org
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spec.ottr.xyz spec.ottr.xyz
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ottr.xyz ottr.xyz
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format.digitallinguistics.io format.digitallinguistics.ioSchemas1
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www.allocine.fr www.allocine.fr
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journal.code4lib.org journal.code4lib.org
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www.slideshare.net www.slideshare.net
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www.dataversity.net www.dataversity.net
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www.w3.org www.w3.org
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www.w3.org www.w3.org
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www.allocine.fr www.allocine.fr
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www.ratp.fr www.ratp.fr
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www.w3.org www.w3.org
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speca.io speca.io
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w3c.github.io w3c.github.io
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www.developerway.com www.developerway.com
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Context selectors, however, could be faked with the use of higher-order components and React.memo.
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There is no way to prevent a component that uses a portion of Context value from re-rendering, even if the used piece of data hasn’t changed, even with useMemo hook.
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✅ Preventing Context re-renders: Context selectors
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If Context manages a few independent data chunks, they can be split into smaller providers under the same provider. That way, only consumers of changed chunk will re-render.
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✅ Preventing Context re-renders: splitting data into chunks
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That way, components that use API only won’t re-render when the data changes.
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If in Context there is a combination of data and API (getters and setters) they can be split into different Providers under the same component. That way, components that use API only won’t re-render when the data changes.
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✅ Preventing Context re-renders: splitting data and API
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If Context Provider is placed not at the very root of the app, and there is a possibility it can re-render itself because of changes in its ancestors, its value should be memoized.
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✅ Preventing Context re-renders: memoizing Provider value
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Preventing re-renders caused by Context
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⛔️ Antipattern: random value as key in lists
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if the list is static, i.e. elements are not added/removed/inserted/re-ordered
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It is okay to use array’s index as key, if the list is static, i.e. elements are not added/removed/inserted/re-ordered.
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Value in key should be a string, that is consistent between re-renders for every element in the list.
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Important: just providing key attribute will not improve lists' performance. To prevent re-renders of list elements you need to wrap them in React.memo and follow all of its best practices.
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Improving re-render performance of lists
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the typical use case for useMemo would be to memoize React elements. Usually parts of an existing render tree or results of generated render tree, like a map function that returns new elements
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useMemo has its cost (consumes a bit of memory and makes initial render slightly slower)
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✅ useMemo for expensive calculations
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If a component uses non-primitive value as a dependency in hooks like useEffect, useMemo, useCallback, it should be memoized.
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If a child component is wrapped in React.memo, all props that are not primitive values have to be memoized
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✅ Necessary useMemo/useCallback
<br/>
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⛔️ Antipattern: unnecessary useMemo/useCallback on props
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If a parent component re-renders, it will trigger re-render of a child component regardless of its props.
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Memoizing props by themselves will not prevent re-renders of a child component.
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React.memo has to be applied to the elements passed as children/props.
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✅ React.memo: components as props or children
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All props that are not primitive values have to be memoized for React.memo to work
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✅ React.memo: component with props
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Wrapping a component in React.memo will stop the downstream chain of re-renders that is triggered somewhere up the render tree, unless this component’s props have changed.
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Preventing re-renders with React.memo
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Props are not affected by the state change, so heavy components won’t re-render
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encapsulates the state inside a smaller component, and heavy components are passed to it as props
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✅ Preventing re-renders with composition: components as props
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✅ Preventing re-renders with composition: children as props
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✅ Preventing re-renders with composition: moving state down
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There is also a big myth: that re-renders happen when the component’s props change. By itself, it’s not true (see the explanation below).
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hooks changes
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context changes
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parent (or children) re-renders
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state changes
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There are four reasons why a component would re-render itself:
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www.netflix.com www.netflix.com
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www.netflix.com www.netflix.com
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socialhub.activitypub.rocks socialhub.activitypub.rocks
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gallica.bnf.fr gallica.bnf.fr
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gallica.bnf.fr gallica.bnf.fr
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gallica.bnf.fr gallica.bnf.fr
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gallica.bnf.fr gallica.bnf.fr
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www.allocine.fr www.allocine.frCarlos1
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www.allocine.fr www.allocine.frCarlos1
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linked.md linked.md
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www.crossref.org www.crossref.org
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www.crossref.org www.crossref.org
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bmcbioinformatics.biomedcentral.com bmcbioinformatics.biomedcentral.com
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linkml.io linkml.io
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www.allocine.fr www.allocine.fr
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paris-bise-art.blogspot.com paris-bise-art.blogspot.com
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codesandbox.io codesandbox.io
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macaroons.io macaroons.io
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hackingdistributed.com hackingdistributed.com
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gist.github.com gist.github.com
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soundcloud.com soundcloud.com
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developer.chrome.com developer.chrome.com
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wicg.github.io wicg.github.io
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developer.chrome.com developer.chrome.com
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developer.chrome.com developer.chrome.com
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wordpress.org wordpress.org
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github.com github.com
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easywpguide.com easywpguide.com
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developers.cloudflare.com developers.cloudflare.com
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solidproject.org solidproject.org
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socialhub.activitypub.rocks socialhub.activitypub.rocks
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www.scitepress.org www.scitepress.org
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mastodonpy.readthedocs.io mastodonpy.readthedocs.io
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www.etsi.org www.etsi.org
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blog.archive.org blog.archive.org
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blog.cloudflare.com blog.cloudflare.com
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www.manton.org www.manton.org
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addons.thunderbird.net addons.thunderbird.net
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soundcloud.com soundcloud.com
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www.youtube.com www.youtube.com
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addons.thunderbird.net addons.thunderbird.net
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www.intra2net.com www.intra2net.com()1
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www.semanticdesktop.org www.semanticdesktop.org
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oscaf.sourceforge.net oscaf.sourceforge.net
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www.semanticdesktop.org www.semanticdesktop.org
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www.youtube.com www.youtube.com
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soundcloud.com soundcloud.com
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globaldjmix.com globaldjmix.com
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