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NickGerleman merged 3 commits into from
Jul 8, 2023
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Update FlatList Optimization Guide for FCs #3700

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Update FlatList Optimization Guide for FCs
Azelisi Apr 24, 2023
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fix lint
Azelisi Apr 24, 2023
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Update docs/optimizing-flatlist-configuration.md
NickGerleman Jul 8, 2023
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24 changes: 19 additions & 5 deletions docs/optimizing-flatlist-configuration.md
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -93,16 +93,30 @@ The more complex your components are, the slower they will render. Try to avoid

The heavier your components are, the slower they render. Avoid heavy images (use a cropped version or thumbnail for list items, as small as possible). Talk to your design team, use as little effects and interactions and information as possible in your list. Show them in your item's detail.

### Use shouldComponentUpdate
### Use `memo()`

Implement update verification to your components. React's `PureComponent` implement a [`shouldComponentUpdate`](https://reactjs.org/docs/react-component.html#shouldcomponentupdate) with shallow comparison. This is expensive here because it needs to check all your props. If you want a good bit-level performance, create the strictest rules for your list item components, checking only props that could potentially change. If your list is basic enough, you could even use
`React.memo()` creates a memoized component that will be re-rendered only when the props passed to the component change. We can use this function to optimize the components in the FlatList.

```tsx
shouldComponentUpdate() {
return false
}
import React, {memo} from 'react';
import {View, Text} from 'react-native';

const MyListItem = memo(
({title}: {title: string}) => (
<View>
<Text>{title}</Text>
</View>
),
(prevProps, nextProps) => {
return prevProps.title === nextProps.title;
},
);

export default MyListItem;
```

In this example, we have determined that MyListItem should be re-rendered only when the title changes. We passed the comparison function as the second argument to React.memo() so that the component is re-rendered only when the specified prop is changed. If the comparison function returns true, the component will not be re-rendered.

### Use cached optimized images

You can use the community packages (such as [react-native-fast-image](https://github.com/DylanVann/react-native-fast-image) from [@DylanVann](https://github.com/DylanVann)) for more performant images. Every image in your list is a `new Image()` instance. The faster it reaches the `loaded` hook, the faster your JavaScript thread will be free again.
Expand Down
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
Update FlatList Optimization Guide for FCs by Azelisi · Pull Request #3700 · react/react-native-website · GitHub
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Update FlatList Optimization Guide for FCs#3700

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NickGerleman
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Jul 8, 2023
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Update FlatList Optimization Guide for FCs
#3700
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Update FlatList Optimization Guide for FCs


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fix lint


Azelisi Apr 24, 2023
f7c7c67

Update docs/optimizing-flatlist-configuration.md


NickGerleman Jul 8, 2023

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24 changes: 19 additions & 5 deletions
docs/optimizing-flatlist-configuration.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -93,16 +93,30 @@ The more complex your components are, the slower they will render. Try to avoid

The heavier your components are, the slower they render. Avoid heavy images (use a cropped version or thumbnail for list items, as small as possible). Talk to your design team, use as little effects and interactions and information as possible in your list. Show them in your item's detail.

### Use shouldComponentUpdate
### Use `memo()`

Implement update verification to your components. React's `PureComponent` implement a [`shouldComponentUpdate`](https://reactjs.org/docs/react-component.html#shouldcomponentupdate) with shallow comparison. This is expensive here because it needs to check all your props. If you want a good bit-level performance, create the strictest rules for your list item components, checking only props that could potentially change. If your list is basic enough, you could even use
`React.memo()` creates a memoized component that will be re-rendered only when the props passed to the component change. We can use this function to optimize the components in the FlatList.

```tsx
shouldComponentUpdate() {
 return false
}
import React, {memo} from 'react';
import {View, Text} from 'react-native';

const MyListItem = memo(
 ({title}: {title: string}) => (
 <View>
 <Text>{title}</Text>
 </View>
 ),
 (prevProps, nextProps) => {
 return prevProps.title === nextProps.title;
 },
);

export default MyListItem;
```

In this example, we have determined that MyListItem should be re-rendered only when the title changes. We passed the comparison function as the second argument to React.memo() so that the component is re-rendered only when the specified prop is changed. If the comparison function returns true, the component will not be re-rendered.

### Use cached optimized images

You can use the community packages (such as [react-native-fast-image](https://github.com/DylanVann/react-native-fast-image) from [@DylanVann](https://github.com/DylanVann)) for more performant images. Every image in your list is a `new Image()` instance. The faster it reaches the `loaded` hook, the faster your JavaScript thread will be free again.
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Update FlatList Optimization Guide for FCs by Azelisi · Pull Request #3700 · react/react-native-website · GitHub
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Update FlatList Optimization Guide for FCs#3700

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 Merged

NickGerleman
merged 3 commits into

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Jul 8, 2023
 Merged


Update FlatList Optimization Guide for FCs
#3700
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369672d

Update FlatList Optimization Guide for FCs


Azelisi Apr 24, 2023
b256a0c

fix lint


Azelisi Apr 24, 2023
f7c7c67

Update docs/optimizing-flatlist-configuration.md


NickGerleman Jul 8, 2023

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24 changes: 19 additions & 5 deletions
docs/optimizing-flatlist-configuration.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -93,16 +93,30 @@ The more complex your components are, the slower they will render. Try to avoid

The heavier your components are, the slower they render. Avoid heavy images (use a cropped version or thumbnail for list items, as small as possible). Talk to your design team, use as little effects and interactions and information as possible in your list. Show them in your item's detail.

### Use shouldComponentUpdate
### Use `memo()`

Implement update verification to your components. React's `PureComponent` implement a [`shouldComponentUpdate`](https://reactjs.org/docs/react-component.html#shouldcomponentupdate) with shallow comparison. This is expensive here because it needs to check all your props. If you want a good bit-level performance, create the strictest rules for your list item components, checking only props that could potentially change. If your list is basic enough, you could even use
`React.memo()` creates a memoized component that will be re-rendered only when the props passed to the component change. We can use this function to optimize the components in the FlatList.

```tsx
shouldComponentUpdate() {
 return false
}
import React, {memo} from 'react';
import {View, Text} from 'react-native';

const MyListItem = memo(
 ({title}: {title: string}) => (
 <View>
 <Text>{title}</Text>
 </View>
 ),
 (prevProps, nextProps) => {
 return prevProps.title === nextProps.title;
 },
);

export default MyListItem;
```

In this example, we have determined that MyListItem should be re-rendered only when the title changes. We passed the comparison function as the second argument to React.memo() so that the component is re-rendered only when the specified prop is changed. If the comparison function returns true, the component will not be re-rendered.

### Use cached optimized images

You can use the community packages (such as [react-native-fast-image](https://github.com/DylanVann/react-native-fast-image) from [@DylanVann](https://github.com/DylanVann)) for more performant images. Every image in your list is a `new Image()` instance. The faster it reaches the `loaded` hook, the faster your JavaScript thread will be free again.
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Update FlatList Optimization Guide for FCs by Azelisi · Pull Request #3700 · react/react-native-website · GitHub
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Update FlatList Optimization Guide for FCs#3700

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 Merged

NickGerleman
merged 3 commits into

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Jul 8, 2023
 Merged


Update FlatList Optimization Guide for FCs
#3700
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369672d

Update FlatList Optimization Guide for FCs


Azelisi Apr 24, 2023
b256a0c

fix lint


Azelisi Apr 24, 2023
f7c7c67

Update docs/optimizing-flatlist-configuration.md


NickGerleman Jul 8, 2023

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24 changes: 19 additions & 5 deletions
docs/optimizing-flatlist-configuration.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -93,16 +93,30 @@ The more complex your components are, the slower they will render. Try to avoid

The heavier your components are, the slower they render. Avoid heavy images (use a cropped version or thumbnail for list items, as small as possible). Talk to your design team, use as little effects and interactions and information as possible in your list. Show them in your item's detail.

### Use shouldComponentUpdate
### Use `memo()`

Implement update verification to your components. React's `PureComponent` implement a [`shouldComponentUpdate`](https://reactjs.org/docs/react-component.html#shouldcomponentupdate) with shallow comparison. This is expensive here because it needs to check all your props. If you want a good bit-level performance, create the strictest rules for your list item components, checking only props that could potentially change. If your list is basic enough, you could even use
`React.memo()` creates a memoized component that will be re-rendered only when the props passed to the component change. We can use this function to optimize the components in the FlatList.

```tsx
shouldComponentUpdate() {
 return false
}
import React, {memo} from 'react';
import {View, Text} from 'react-native';

const MyListItem = memo(
 ({title}: {title: string}) => (
 <View>
 <Text>{title}</Text>
 </View>
 ),
 (prevProps, nextProps) => {
 return prevProps.title === nextProps.title;
 },
);

export default MyListItem;
```

In this example, we have determined that MyListItem should be re-rendered only when the title changes. We passed the comparison function as the second argument to React.memo() so that the component is re-rendered only when the specified prop is changed. If the comparison function returns true, the component will not be re-rendered.

### Use cached optimized images

You can use the community packages (such as [react-native-fast-image](https://github.com/DylanVann/react-native-fast-image) from [@DylanVann](https://github.com/DylanVann)) for more performant images. Every image in your list is a `new Image()` instance. The faster it reaches the `loaded` hook, the faster your JavaScript thread will be free again.
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
Update FlatList Optimization Guide for FCs by Azelisi · Pull Request #3700 · react/react-native-website · GitHub
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Update FlatList Optimization Guide for FCs#3700

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 Merged

NickGerleman
merged 3 commits into

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Jul 8, 2023
 Merged


Update FlatList Optimization Guide for FCs
#3700
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369672d

Update FlatList Optimization Guide for FCs


Azelisi Apr 24, 2023
b256a0c

fix lint


Azelisi Apr 24, 2023
f7c7c67

Update docs/optimizing-flatlist-configuration.md


NickGerleman Jul 8, 2023

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24 changes: 19 additions & 5 deletions
docs/optimizing-flatlist-configuration.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -93,16 +93,30 @@ The more complex your components are, the slower they will render. Try to avoid

The heavier your components are, the slower they render. Avoid heavy images (use a cropped version or thumbnail for list items, as small as possible). Talk to your design team, use as little effects and interactions and information as possible in your list. Show them in your item's detail.

### Use shouldComponentUpdate
### Use `memo()`

Implement update verification to your components. React's `PureComponent` implement a [`shouldComponentUpdate`](https://reactjs.org/docs/react-component.html#shouldcomponentupdate) with shallow comparison. This is expensive here because it needs to check all your props. If you want a good bit-level performance, create the strictest rules for your list item components, checking only props that could potentially change. If your list is basic enough, you could even use
`React.memo()` creates a memoized component that will be re-rendered only when the props passed to the component change. We can use this function to optimize the components in the FlatList.

```tsx
shouldComponentUpdate() {
 return false
}
import React, {memo} from 'react';
import {View, Text} from 'react-native';

const MyListItem = memo(
 ({title}: {title: string}) => (
 <View>
 <Text>{title}</Text>
 </View>
 ),
 (prevProps, nextProps) => {
 return prevProps.title === nextProps.title;
 },
);

export default MyListItem;
```

In this example, we have determined that MyListItem should be re-rendered only when the title changes. We passed the comparison function as the second argument to React.memo() so that the component is re-rendered only when the specified prop is changed. If the comparison function returns true, the component will not be re-rendered.

### Use cached optimized images

You can use the community packages (such as [react-native-fast-image](https://github.com/DylanVann/react-native-fast-image) from [@DylanVann](https://github.com/DylanVann)) for more performant images. Every image in your list is a `new Image()` instance. The faster it reaches the `loaded` hook, the faster your JavaScript thread will be free again.
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Update FlatList Optimization Guide for FCs by Azelisi · Pull Request #3700 · react/react-native-website · GitHub
Skip to content
Update FlatList Optimization Guide for FCs#3700

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 Merged

NickGerleman
merged 3 commits into

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Jul 8, 2023
 Merged


Update FlatList Optimization Guide for FCs
#3700
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369672d

Update FlatList Optimization Guide for FCs


Azelisi Apr 24, 2023
b256a0c

fix lint


Azelisi Apr 24, 2023
f7c7c67

Update docs/optimizing-flatlist-configuration.md


NickGerleman Jul 8, 2023

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24 changes: 19 additions & 5 deletions
docs/optimizing-flatlist-configuration.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -93,16 +93,30 @@ The more complex your components are, the slower they will render. Try to avoid

The heavier your components are, the slower they render. Avoid heavy images (use a cropped version or thumbnail for list items, as small as possible). Talk to your design team, use as little effects and interactions and information as possible in your list. Show them in your item's detail.

### Use shouldComponentUpdate
### Use `memo()`

Implement update verification to your components. React's `PureComponent` implement a [`shouldComponentUpdate`](https://reactjs.org/docs/react-component.html#shouldcomponentupdate) with shallow comparison. This is expensive here because it needs to check all your props. If you want a good bit-level performance, create the strictest rules for your list item components, checking only props that could potentially change. If your list is basic enough, you could even use
`React.memo()` creates a memoized component that will be re-rendered only when the props passed to the component change. We can use this function to optimize the components in the FlatList.

```tsx
shouldComponentUpdate() {
 return false
}
import React, {memo} from 'react';
import {View, Text} from 'react-native';

const MyListItem = memo(
 ({title}: {title: string}) => (
 <View>
 <Text>{title}</Text>
 </View>
 ),
 (prevProps, nextProps) => {
 return prevProps.title === nextProps.title;
 },
);

export default MyListItem;
```

In this example, we have determined that MyListItem should be re-rendered only when the title changes. We passed the comparison function as the second argument to React.memo() so that the component is re-rendered only when the specified prop is changed. If the comparison function returns true, the component will not be re-rendered.

### Use cached optimized images

You can use the community packages (such as [react-native-fast-image](https://github.com/DylanVann/react-native-fast-image) from [@DylanVann](https://github.com/DylanVann)) for more performant images. Every image in your list is a `new Image()` instance. The faster it reaches the `loaded` hook, the faster your JavaScript thread will be free again.
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Update FlatList Optimization Guide for FCs by Azelisi · Pull Request #3700 · react/react-native-website · GitHub
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Update FlatList Optimization Guide for FCs#3700

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NickGerleman
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Jul 8, 2023
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Update FlatList Optimization Guide for FCs
#3700
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369672d

Update FlatList Optimization Guide for FCs


Azelisi Apr 24, 2023
b256a0c

fix lint


Azelisi Apr 24, 2023
f7c7c67

Update docs/optimizing-flatlist-configuration.md


NickGerleman Jul 8, 2023

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24 changes: 19 additions & 5 deletions
docs/optimizing-flatlist-configuration.md

View file


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Original file line numberDiff line numberDiff line change
Expand Up@@ -93,16 +93,30 @@ The more complex your components are, the slower they will render. Try to avoid

The heavier your components are, the slower they render. Avoid heavy images (use a cropped version or thumbnail for list items, as small as possible). Talk to your design team, use as little effects and interactions and information as possible in your list. Show them in your item's detail.

### Use shouldComponentUpdate
### Use `memo()`

Implement update verification to your components. React's `PureComponent` implement a [`shouldComponentUpdate`](https://reactjs.org/docs/react-component.html#shouldcomponentupdate) with shallow comparison. This is expensive here because it needs to check all your props. If you want a good bit-level performance, create the strictest rules for your list item components, checking only props that could potentially change. If your list is basic enough, you could even use
`React.memo()` creates a memoized component that will be re-rendered only when the props passed to the component change. We can use this function to optimize the components in the FlatList.

```tsx
shouldComponentUpdate() {
 return false
}
import React, {memo} from 'react';
import {View, Text} from 'react-native';

const MyListItem = memo(
 ({title}: {title: string}) => (
 <View>
 <Text>{title}</Text>
 </View>
 ),
 (prevProps, nextProps) => {
 return prevProps.title === nextProps.title;
 },
);

export default MyListItem;
```

In this example, we have determined that MyListItem should be re-rendered only when the title changes. We passed the comparison function as the second argument to React.memo() so that the component is re-rendered only when the specified prop is changed. If the comparison function returns true, the component will not be re-rendered.

### Use cached optimized images

You can use the community packages (such as [react-native-fast-image](https://github.com/DylanVann/react-native-fast-image) from [@DylanVann](https://github.com/DylanVann)) for more performant images. Every image in your list is a `new Image()` instance. The faster it reaches the `loaded` hook, the faster your JavaScript thread will be free again.
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
Update FlatList Optimization Guide for FCs by Azelisi · Pull Request #3700 · react/react-native-website · GitHub
Skip to content
Update FlatList Optimization Guide for FCs#3700

New issue

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 Merged

NickGerleman
merged 3 commits into

from

Jul 8, 2023
 Merged


Update FlatList Optimization Guide for FCs
#3700
 Changes from all commits
Commits

Show all changes


3 commits


Select commit
Hold shift + click to select a range
369672d

Update FlatList Optimization Guide for FCs


Azelisi Apr 24, 2023
b256a0c

fix lint


Azelisi Apr 24, 2023
f7c7c67

Update docs/optimizing-flatlist-configuration.md


NickGerleman Jul 8, 2023

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24 changes: 19 additions & 5 deletions
docs/optimizing-flatlist-configuration.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -93,16 +93,30 @@ The more complex your components are, the slower they will render. Try to avoid

The heavier your components are, the slower they render. Avoid heavy images (use a cropped version or thumbnail for list items, as small as possible). Talk to your design team, use as little effects and interactions and information as possible in your list. Show them in your item's detail.

### Use shouldComponentUpdate
### Use `memo()`

Implement update verification to your components. React's `PureComponent` implement a [`shouldComponentUpdate`](https://reactjs.org/docs/react-component.html#shouldcomponentupdate) with shallow comparison. This is expensive here because it needs to check all your props. If you want a good bit-level performance, create the strictest rules for your list item components, checking only props that could potentially change. If your list is basic enough, you could even use
`React.memo()` creates a memoized component that will be re-rendered only when the props passed to the component change. We can use this function to optimize the components in the FlatList.

```tsx
shouldComponentUpdate() {
 return false
}
import React, {memo} from 'react';
import {View, Text} from 'react-native';

const MyListItem = memo(
 ({title}: {title: string}) => (
 <View>
 <Text>{title}</Text>
 </View>
 ),
 (prevProps, nextProps) => {
 return prevProps.title === nextProps.title;
 },
);

export default MyListItem;
```

In this example, we have determined that MyListItem should be re-rendered only when the title changes. We passed the comparison function as the second argument to React.memo() so that the component is re-rendered only when the specified prop is changed. If the comparison function returns true, the component will not be re-rendered.

### Use cached optimized images

You can use the community packages (such as [react-native-fast-image](https://github.com/DylanVann/react-native-fast-image) from [@DylanVann](https://github.com/DylanVann)) for more performant images. Every image in your list is a `new Image()` instance. The faster it reaches the `loaded` hook, the faster your JavaScript thread will be free again.
Expand Down