Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
React Native: Under the Hood
Search
Alexander Kotliarskyi
June 09, 2015
Programming
31
22k
React Native: Under the Hood
Alexander Kotliarskyi
June 09, 2015
Tweet
Share
More Decks by Alexander Kotliarskyi
See All by Alexander Kotliarskyi
Building Stellar User Experiences with React Native
frantic
2
950
React Native Tutorial - NYC'15
frantic
5
1.4k
Other Decks in Programming
See All in Programming
もうちょっといいRubyプロファイラを作りたい (2025)
osyoyu
0
300
Microsoft Orleans, Daprのアクターモデルを使い効率的に開発、デプロイを行うためのSekibanの試行錯誤 / Sekiban: Exploring Efficient Development and Deployment with Microsoft Orleans and Dapr Actor Models
tomohisa
0
240
2025 年のコーディングエージェントの現在地とエンジニアの仕事の変化について
azukiazusa1
18
9.4k
ECS初心者の仲間 – TUIツール「e1s」の紹介
keidarcy
0
150
Processing Gem ベースの、2D レトロゲームエンジンの開発
tokujiros
2
120
FindyにおけるTakumi活用と脆弱性管理のこれから
rvirus0817
0
420
機能追加とリーダー業務の類似性
rinchoku
2
1.1k
The Past, Present, and Future of Enterprise Java
ivargrimstad
0
230
[FEConf 2025] 모노레포 절망편, 14개 레포로 부활하기까지 걸린 1년
mmmaxkim
0
1.5k
rage against annotate_predecessor
junk0612
0
160
MCPとデザインシステムに立脚したデザインと実装の融合
yukukotani
4
1.3k
テストカバレッジ100%を10年続けて得られた学びと品質
mottyzzz
2
480
Featured
See All Featured
Helping Users Find Their Own Way: Creating Modern Search Experiences
danielanewman
29
2.8k
Art, The Web, and Tiny UX
lynnandtonic
302
21k
The World Runs on Bad Software
bkeepers
PRO
70
11k
Practical Tips for Bootstrapping Information Extraction Pipelines
honnibal
PRO
23
1.4k
[Rails World 2023 - Day 1 Closing Keynote] - The Magic of Rails
eileencodes
36
2.5k
Being A Developer After 40
akosma
90
590k
Large-scale JavaScript Application Architecture
addyosmani
512
110k
Reflections from 52 weeks, 52 projects
jeffersonlam
352
21k
It's Worth the Effort
3n
187
28k
Unsuck your backbone
ammeep
671
58k
Easily Structure & Communicate Ideas using Wireframe
afnizarnur
194
16k
Exploring the Power of Turbo Streams & Action Cable | RailsConf2023
kevinliebholz
34
6k
Transcript
React Native: Under the hood Alex Kotliarskyi Facebook
Plan 1. Why native apps matter? 2. How ReactJS works
3. Running ReactJS on native platforms
Why do we ❤ native apps?
Native Apps • Fast, responsive • Complex gestures and smooth
animations • Consistent with platform
None
Building native apps is hard • Different stacks of technologies
• No knowledge and code sharing • Slow iteration speed • Hard to scale
Web got this right
Web • Different stacks of technologies • No knowledge and
code sharing • Slow iteration speed • Hard to scale HTML / CSS / JS Same code and tech F5 / ⌘R React!
Web apps on the phone are not great • Very
hard to provide smooth experiences • Not designed for complex interactions • Impossible to embed native components
Development experience Awesome apps
React Native
None
UI = ƒ*(data) * No side effects
None
UI = ƒ(count)
UI = ƒ(count) = div( span('Count ' + count), button('Add
+1') )
render() { return (
div( span( 'Count: ' + b(this.state.count) ), button( 'Add +1' ) ) ) }
render() { return (
<div> <span> Count: <b>{this.state.count}</b> </span> <button> Add +1 </button> </div> ) } HTML VirtualDOM
render() { return (
<div> <span> Count: <b>{this.state.count}</b> </span> <button onClick={() => ??? }> Add +1 </button> </div> ) }
TextView text = (TextView)findViewByID(R.layout.label); text.setText('10'); _label.text = @"10"; too
complex Android Objective-C JavaScript document.getElementByID('count').children[1].innerHTML = '10'; $('#counter b').html('10');
render() { var count = this.state.count;
return ( <div> <span> Count: <b>{count}</b> </span> <button onClick={() => ??? }> Add +1 </button> </div> ) }
render() { var count = this.state.count;
return ( <div> <span> Count: <b>{count}</b> </span> <button onClick={() => this.setState({count: count + 1})}> Add +1 </button> </div> ) } setState
setState
<div> <span>
Count: <b>9</b> </span> <button> Add +1 </button> </div> <div> <span> Count: <b>10</b> </span> <button> Add +1 </button> </div> state = {count: 9} state = {count: 10} <b>9</b> <b>9</b> <b>10</b> findDOMNode(b).innerHTML = '10';
Components Browser DOM UIKit Components Components Components VirtualDOM
1. Runtime 2.Base components 3. Calling native functions
ECMAScript 5
JavaScript Core • Part of WebKit project • Open Source
• Ships with iOS Runtime
<div> <span> <img> <View> <Text> <Image>
<ScrollView> <MapView> <TabBar> <DatePicker> ... Base components
create(view, parent, attributes)* update(view, attributes) delete(view) * actually React is
more complex that that
Just call native functions? nope
Synchronous
Native Method JavaScript time Waiting…
JavaScript time Native JavaScript Native
Synchronous Asynchronous
Overhead of every native call
JavaScript time
time JavaScript
Overhead of every native call Batch native calls
Shared mutable data
Native Objects JavaScript Objects
Shared mutable data Exchange serializable messages
Asynchronous Batched Serializable
The Bridge
Native Bridge JavaScript
Native Bridge JavaScript Event (touch, timer, networks, etc.) 1 Collect
data and notify JS 2 Serialized payload 3 Process event 4 Call 0 – ∞ native methods 5 Update UI (if needed) 8 Serialized response 6 Process commands 7
JS is event-driven
Events Commands
Example
• Updates counter • Sends data to web service
render() { return (
<View style={styles.container}> <Text style={styles.value}> {this.state.count} </Text> <Button title="Add +1" onPress={() => this.inc()} /> </View> ); }
inc() { var newCount =
this.state.count + 1; this.setState({count: newCount}); fetch( 'https://api.conunter.io/', { method: 'post', body: 'value=' + newCount } ); }
Native UITouch [_bridge enqueueJSCall:@"EventEmitter.receiveTouches" args:@[@"end", @{@"x": @42, @"y": @106}]]; x,
y, view, ...
Native Bridge JavaScript [ 'EventEmitter', 'receiveTouches', ['end', {'x': 42, 'y':
106}] ] [_bridge enqueueJSCall:@"RCTEventEmitter.receiveTouches" args:@[@"end", @{@"x": @42, @"y": @106}]]; call('EventEmitter', 'receiveTouches', [{x: 42, y: ...}])
function call(moduleName, methodName, args) { MessageQueue.init();
var module = require(moduleName); module[methodName].apply(module, args); return MessageQueue.flush(); } // EventEmitter // receiveTouches Message queue
Touch processing
What element should respond to a given event?
Button Button pressed!
Button Cancelled
Button Cancelled Scrollview
Button Scrolling stops Scrollview
Button Scrollview Horizontal Scrollview Navigator
Responder System
onStartShouldSetResponder onResponderTerminationRequest onResponderGrant onResponderMove onResponderRelease onResponderTerminate …
<TouchableOpacity> <TouchableHighlight> <TouchableBounce> <TouchableWithoutFeedback> onPress
inc() { var newCount =
this.state.count + 1; this.setState({count: newCount}); fetch( 'https://api.conunter.io/', { method: 'post', body: 'value=' + newCount } ); }
<View style={...}>
<Text style={...}> 42 </Text> <Button title="Add +1" onPress={...} /> </View> <View style={...}> <Text style={...}> 43 </Text> <Button title="Add +1" onPress={...} /> </View> 42 43
var UIManager = require('NativeModules').UIManager; UIManager.update(18, {text: '43'}); Somewhere in
React's internals:
NativeModules
NativeModules.UIManager = { ... update: function(viewID,
attributes) { MessageQueue.push( ['UIManager', 'update', [viewID, attributes]] ); } ... }; Message queue UIManager update ..
inc() { var newCount =
this.state.count + 1; this.setState({count: newCount}); fetch( 'https://api.conunter.io/', { method: 'post', body: 'value=' + newCount } ); } Message queue UIManager update .. DataManager query ....
function call(moduleName, methodName, args) { MessageQueue.init();
var module = require(moduleName); module[methodName].apply(module, args); return MessageQueue.flush(); } Message queue UIManager update .. DataManager query ....
Native Bridge JavaScript [UIManager updateView:18 props:@{@"text": @"43"}] [DataManager query:@"post" url:@"http://..."]
[ ['UIManager', 'update', [18, {text: '43'}]], ['DataManager', 'query', ['post', 'http://...']] ] Message queue UIManager update .. DataManager query ....
Native [UIManager updateView:18 props:@{@"text": @"43"}] addUIBlock:^() { UILabel *label =
viewRegistry[18]; label.text = @"43"; [label markAsDirty]; }
Layout Layout github.com/facebook/css-layout
{ margin: 20, borderBottomWidth: 2, flex: 1, alignContent: 'center', }
{ left: 120, top: 220, width: 60, height: 60, } Flexbox Coordinates
• User taps the button • Counter is updated
Native Bridge JavaScript Event (touch, timer, networks, etc.) 1 Collect
data and notify JS 2 Serialized payload 3 Process event 4 Call 0 – ∞ native methods 5 Serialized response 6 Process commands 7 Update UI (if needed) 8
Benefits
Fast
Native Bridge JavaScript Event (touch, timer, networks, etc.) 1 Update
UI (if needed) 8 Collect data and notify JS 2 Serialized payload 3 Process event 4 Call 0 – ∞ native methods 5 Serialized response 6 Process commands 7
Record / Replay
Flexible JS runtime
Native Bridge JavaScript
Native Bridge JavaScript Awesome App
Native Bridge JavaScript Awesome App WebKit process IPC
Native Bridge JavaScript Awesome App Chrome Debugger WebSockets
Live demo iPhone -> Chrome
None
None
Heroku iPhone
Streaming
None
UI = ƒ(data)
Thank you! github.com/frantic/tlv-2015 @alex_frantic