Smells in React Apps

Thai Pangsakulyanont 1 Smells in React Apps JSConf.Asia 2018

Slide № 2

Slide № 3 Sawasdee krub (Hello in Thai)

Slide № 4 Smells in React Apps

Slide № 5 Refactoring: Improving the Design of Existing Code
Clean Code: A Handbook of Agile Software Craftsmanship Agile Software Development, Principles, Patterns, and Practices

Slide № 6 (Contents afterwards are mainly based on my
experience.)

About Me Slide № 7 Thai Pangsakulyanont (@dtinth)

Slide № 8

Slide № 9 Loves to build software for fun.

Slide № 10 dtinth/midi-instruments https://302.dt.in.th/midi-instruments-pv

Slide № 11 dtinth/atom-aesthetic-ui

Slide № 12 dtinth/atom-aesthetic-ui

Slide № 13 dtinth/GyroscratchAndroid bemusic/gyroscratch-web https://302.dt.in.th/gyroscratch-pv

Slide № 14 Loves to build software for fun.

Slide № 15 Interested in the ways  to make software
maintainable.

Slide № 16 One of my old project… (2009)

Slide № 17 7000 lines of untestable code.

Slide № 18 7000 lines of untestable code. Maintain: Not
fun

Slide № 19 7000 lines of untestable code. Maintain: Not
fun Improve the codebase: Not fun

Slide № 20 Development stopped

Slide № 21 Development stopped :(

Slide № 22 What I learned…

Slide № 23 Sustainability matters!

Slide № 24 Interested in the ways  to make software
maintainable.

Slide № 25 Object-oriented analysis and design Clean architecture Functional
programming Automated testing Continuous integration Linting Type systems Modularization Componentization Code smells …

Slide № 26 Later… (2014)

Slide № 27 bemusic/bemuse https://302.dt.in.th/bemuse-pv ADVERTISEMENT https://bemuse.ninja/

Slide № 28

Slide № 29

Slide № 30 Static analysis with ESLint

Slide № 31 Static analysis with ESLint

Slide № 32 Unit testing (Mocha)

Slide № 33 Continuous integration & deployment (CircleCI)

Slide № 34 Code coverage (Codecov)

Slide № 35 3 weeks of project setup

Slide № 36 Result

Slide № 37 :) Unit tests increases confidence when making
a huge change to the codebase.

Slide № 38 Decoupled architecture

Slide № 39 Implementation details behind an interface

Slide № 40 Some features can be prototyped in 1
night

Slide № 41 A good codebase is like a clean
table.

Slide № 42

Slide № 43

Slide № 44

Slide № 45 Present (2018)

Slide № 46 Front-end architect at @taskworld * Opinion expressed
are my own.

Slide № 47 React + Redux

Slide № 48

Slide № 49 Redux store

Slide № 50 Redux store React components

Slide № 51 Redux store React components 900+ components

Slide № 52 Redux store React components 900+ components Over
2 years

Slide № 53 Redux store React components 900+ components Over
2 years, 20+ engineers worked on it

programming Automated testing Continuous integration Linting Type systems Modularization Componentization Code smells …

programming Automated testing Continuous integration Linting Type systems Modularization Componentization Code smells … Tech stuffs

Slide № 56 Communication

Slide № 57 Example

Slide № 58 // MusicPreviewer.js export function preload () {
getInstance() } export function enable () { return getInstance().enable() } export function disable () { return getInstance().disable() } export function go () { return getInstance().go() } export function preview (url) { return getInstance().preview(url) } MusicPreviewer

getInstance() } export function enable () { return getInstance().enable() } export function disable () { return getInstance().disable() } export function go () { return getInstance().go() } export function preview (url) { return getInstance().preview(url) } MusicPreviewer exports 5 functions

getInstance() } export function enable () { return getInstance().enable() } export function disable () { return getInstance().disable() } export function go () { return getInstance().go() } export function preview (url) { return getInstance().preview(url) } import * as MusicPreviewer from MusicPreviewer.preload() MusicPreviewer.enable() MusicPreviewer.disable() MusicPreviewer.go() MusicPreviewer.preview(url) User code:

Slide № 61 Behind the interface

Slide № 62 let instance const getInstance = () =>
instance || ( instance = createMusicPreviewer() ) function createMusicPreviewer () { let enabled = false let currentUrl = null let backgroundLoaded = false let backgroundPlayed = false const instances = {} function update () { if (!enabled) { if (backgroundPlayed) { backgroundFader.fadeTo(0, 100) backgroundPlayed = false background.pause() } for (const key of Object.keys(instances)) { const instance = instances[key] instance.destroy() } return } let playing = null for (const key of Object.keys(instances)) { const instance = instances[key] if (key === currentUrl) { if (instance.loaded) { instance.play() playing = instance } else { instance.stop() } } if (playing) { backgroundFader.fadeTo(0, 1) } else { backgroundFader.fadeTo(0.4, 0.5) if (backgroundLoaded && !backgroundPlayed) { backgroundPlayed = true try { background.play() } catch (e) { console.warn('Cannot play background music') } } } } const musicPreviewer = { enable () { if (enabled) return enabled = true update() }, disable () { if (!enabled) return enabled = false update() }, go () { if (!enabled) return goSound.currentTime = 0

Slide № 63 Wrote a hack behind a well-designed interface
In principle: Bad code stays behind that interface.

In principle: Bad code stays behind that interface. In practice: Another person looks for a technical solution,

In principle: Bad code stays behind that interface. In practice: Another person looks for a technical solution, found my hack (but didn’t know it was a hack),

In principle: Bad code stays behind that interface. In practice: Another person looks for a technical solution, found my hack (but didn’t know it was a hack), and duplicated the code!

Slide № 67 Effective code reviews

Slide № 68 Smells

Slide № 69 Information leaks

Slide № 71 Standard UI kit

Slide № 72 A UserAvatar component

Slide № 73 <UserAvatar size='small' … /> A UserAvatar component

Slide № 74 <UserAvatar size='small' … /> <UserAvatar size='medium' …
/> A UserAvatar component

/> <UserAvatar size='large' … /> A UserAvatar component

Slide № 77 New feature! Messaging system

Slide № 78 Thai Pangsakulyanont 1 minute ago Let’s go
to the Marina Bay Carnival after the conference!!!!

Slide № 79

/> <UserAvatar size='large' … /> A UserAvatar component <UserAvatar size='message' … />

Slide № 84 Few months later

Slide № 85 Few months later everywhere! <UserAvatar size='message' …
/>

Slide № 86 Step out of code Look at the
big picture

Slide № 87 UserAvatar Message

Slide № 88 UserAvatar specific feature Message

Slide № 89 UserAvatar specific feature generic component Message

Slide № 90 UserAvatar specific feature generic component I need
to show an avatar! Message

Slide № 91 UserAvatar uses specific feature generic component Message
I need to show an avatar!

Slide № 92 UserAvatar uses specific feature generic component I
know how big to display in a message Message

Slide № 93 UserAvatar uses aware of specific feature generic
component Message I know how big to display in a message

Slide № 94 UserAvatar uses aware of specific feature generic
component Information leaking. Message

Slide № 95 UserAvatar Message uses aware of specific feature
generic component Information leaking. Knows how to render itself Except: Doesn’t know the appropriate size of the avatar

Slide № 96 UserAvatar Message uses aware of specific feature
generic component Information leaking. Knows how to render itself Except: Doesn’t know the appropriate size of the avatar The knowledge of the size, which should have belonged to the messaging system is here

Slide № 97 Leakage Information about a specific feature leaked
into a generic component

Slide № 98 Generic component not flexible enough.

Slide № 99 Make the generic component more flexible

/> <UserAvatar size='large' … /> A UserAvatar component <UserAvatar size='message' … />

Slide № 101 A UserAvatar component XS S M L
XL XXL XXXL

Slide № 102 UserAvatar specific feature generic component I need
to show an avatar! It’s going to have size M! Message

Slide № 103 A UserAvatar component function UserAvatar (props) {
… } UserAvatar.propTypes = { size: PropTypes.oneOf([ 'XS', 'S', 'M', 'L', 'XL', 'XXL', 'XX … }

… } UserAvatar.propTypes = { size: PropTypes.oneOf([ 'XS', 'S', 'M', 'L', 'XL', 'XXL', 'XX … }

… } UserAvatar.propTypes = { size: PropTypes.number, … }

… } UserAvatar.propTypes = { size: PropTypes.oneOf([ 18, 24, 30, 36, 48, … ]), … }

Slide № 107 Sometimes it’s just naming.

Slide № 109 Standard UI kit

Slide № 110 Upload file

Slide № 113 Upload file Select file on computer… Dropbox
Google Drive Emergency alert

Google Drive Emergency alert Select file on computer…

Google Drive Emergency alert <Button>

Google Drive Emergency alert <Menu> <Button>

Slide № 117 Select file on computer… Dropbox Google Drive
Emergency alert Upload file

Emergency alert <MenuButton> Upload file

Slide № 119 Upload file <MenuButton>

Slide № 120 <MenuButton> Upload file

Emergency alert <MenuButton> Upload file

Emergency alert <MenuButton> Upload file Select file on computer…

Emergency alert <MenuButton> Upload file Select file on computer… Button must appear to be pressed while menu is open

Slide № 124 Upload file <MenuButton>

Slide № 125 Upload file Button.propTypes = { children: PropTypes.node
}

Slide № 126 Upload file Button.propTypes = { children: PropTypes.node,
isMenuOpen: PropTypes.bool }

Slide № 127 Button.propTypes = { children: PropTypes.node, isMenuOpen: PropTypes.bool
} Upload file

} Button is now aware of the menu Upload file

} Upload file

Slide № 130 Button.propTypes = { children: PropTypes.node, isDepressed: PropTypes.bool
} Upload file

Slide № 131 When reviewing code: “Does this really needs
to know about that?”

Slide № 132 Low cohesion

Slide № 133 “Cohesion” Related things stay together.

Slide № 135 A navigation bar

Slide № 136 A navigation bar

Slide № 137 class Navigation extends Component { render ()
{ }

{ return ( <Navbar> </Navbar> ) }

{ return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> </Navbar> ) }

{ return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav> </Navbar> ) }

Slide № 142 New feature!

Slide № 143 New feature! Authentication system

Slide № 144 When logged out When logged in

{ return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav> </Navbar> ) } }

Slide № 147 class Navigation extends Component {   render
() { return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav>

Slide № 148 class Navigation extends Component {  static propTypes
= { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav>

Slide № 149 class Navigation extends Component { static propTypes
= { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav>

Slide № 150 const loggedIn = !!this.props.currentUser return ( <Navbar>
<Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav> </Navbar> ) } }

<Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav> <Nav pullRight> </Nav> </Navbar> ) } }

<Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav> <Nav pullRight> {!loggedIn && <NavItem href='#' onClick={this.props.onLogin}>Login</NavI {loggedIn && <NavItem href='#' onClick={this.props.onLogout}>Logout</Nav </Nav> </Navbar> ) } }

= { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header>

Slide № 154 const enhance = connect( state => ({
currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header>

currentUser: selectCurrentUser(props) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header>

currentUser: selectCurrentUser(props) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> Selecting data from store

currentUser: selectCurrentUser(props) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> Selecting data from store Dispatching action to store

currentUser: selectCurrentUser(props) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> Selecting data from store Dispatching action to store Rendering logic

Slide № 159 New features!

Slide № 160 Notification system Messaging system

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> Selecting data from store Dispatching action to store Rendering logic

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> Selecting data from store Dispatching action to store Rendering logic Go with the flow!

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser

currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser

currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout, onViewMessages: MessagesIO.viewMessages } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser

Slide № 170 onViewMessages: MessagesIO.viewMessages } ) class Navigation extends
Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem>

Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header>

Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header>

Slide № 173 <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand>
</Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav> <Nav pullRight> {!loggedIn && <NavItem href='#' onClick={this.props.onLogin}>Login</NavI {loggedIn && <NavItem href='#' onClick={this.props.onLogout}>Logout</Nav </Nav> </Navbar> ) } }

</Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> </Nav> <Nav pullRight>

</Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> {loggedIn && <NavItem href='/notifications'> Notifications ({this.props.newNotificationCount}) </NavItem> } </Nav> <Nav pullRight>

</Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> {loggedIn && <NavItem href='/notifications'> Notifications ({this.props.newNotificationCount}) </NavItem> } {loggedIn && <NavItem href='/inbox' onClick={this.props.onViewMessages}> Messages ({this.props.newMessageCount}) </NavItem> } </Nav> <Nav pullRight>

currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout, onViewMessages: MessagesIO.viewMessages } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> {loggedIn && <NavItem href='/notifications'> Notifications ({this.props.newNotificationCount})

currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout, onViewMessages: MessagesIO.viewMessages } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> {loggedIn && <NavItem href='/notifications'> Notifications ({this.props.newNotificationCount}) Selecting data from store Dispatching action to store Rendering logic

currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout, onViewMessages: MessagesIO.viewMessages } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> {loggedIn && <NavItem href='/notifications'> Notifications ({this.props.newNotificationCount}) Selecting data from store Dispatching action to store Rendering logic Cross-cutting concerns

Slide № 181 User Notification Message User Message User Notification
Message User Navigation Navigation User Navigation const enhance = connect( state => ({ currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout, onViewMessages: MessagesIO.viewMessages } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> {loggedIn && <NavItem href='/notifications'> Notifications ({this.props.newNotificationCount})

Slide № 182 User Notification Message User Message User Notification
Message User Navigation Navigation User Navigation const enhance = connect( state => ({ currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout, onViewMessages: MessagesIO.viewMessages } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> {loggedIn && <NavItem href='/notifications'> Notifications ({this.props.newNotificationCount})

Slide № 183 Real-world example

Slide № 184 Bemuse options panel

Slide № 185 Bemuse options panel

Slide № 186 diff --git src/app/ui/OptionsPlayer.jsx src/app/ui/OptionsPlayer.jsx index a2e1d2e..2333c9f 100644
--- src/app/ui/OptionsPlayer.jsx +++ src/app/ui/OptionsPlayer.jsx @@ -1,176 +1,191 @@ const enhance = compose( connect((state) => ({ options: state.options, scratch: Options.scratchPosition(state.options), })), connectIO({ onSetPanel: () => (value) => OptionsIO.setOptions({ 'player.P1.panel': value }), onSetScratch: () => (position) => OptionsIO.setScratch(position), onSetSpeed: () => (speed) => OptionsIO.setSpeed(speed), onSetLeadTime: () => (leadTime) => OptionsIO.setLeadTime(leadTime), onSetLaneCover: () => (laneCover) => OptionsIO.setLaneCover(laneCover), onToggleBackgroundAnimationsEnabled: ({ options }) => () => ( OptionsIO.setOptions({ 'system.bga.enabled': Options.toggleOption(options['system.bga.enabled']) }) ), onToggleAutoVelocityEnabled: ({ options }) => () => ( OptionsIO.setOptions({ 'player.P1.auto-velocity': Options.toggleOption(options['player.P1.auto-velocity']) }) ) }), pure ) export const OptionsPlayer = React.createClass({ propTypes: { options: React.PropTypes.object, scratch: React.PropTypes.string, onClose: React.PropTypes.func, onSetPanel: React.PropTypes.func, onSetScratch: React.PropTypes.func, onSetSpeed: React.PropTypes.func, onSetLaneCover: React.PropTypes.func, onToggleBackgroundAnimationsEnabled: React.PropTypes.func, onToggleAutoVelocityEnabled: React.PropTypes.func, onSetLeadTime: React.PropTypes.func }, render () { return <div className="OptionsPlayer"> <OptionsPlayer.Row label="Speed" hidden={Options.isAutoVelocityEnabled(this.props.options)} > <OptionsSpeed value={this.props.options['player.P1.speed']} onChange={this.props.onSetSpeed} /> <div className="OptionsPlayerͷhelp"> You can also change the speed in-game<br />using the Up and Down arrow keys. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="LeadTime" hidden={!Options.isAutoVelocityEnabled(this.props.options)} > <OptionsLeadTimeInputField value={Options.leadTime(this.props.options)} onChange={this.props.onSetLeadTime} style={{ width: '5em' }} /> <div className="OptionsPlayerͷhelp"> Speed will be automatically adjusted<br />to maintain a consistent note velocity. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="Scratch"> <OptionsPlayerSelector type="scratch" options={SCRATCH_OPTIONS} onSelect={this.props.onSetScratch} value={this.props.scratch} /> </OptionsPlayer.Row> <OptionsPlayer.Row label="Panel"> <OptionsPlayerSelector type="panel" options={PANEL_OPTIONS} onSelect={this.props.onSetPanel} value={this.props.options['player.P1.panel']} /> </OptionsPlayer.Row> <OptionsPlayer.Row label="Cover"> <OptionsLaneCoverInputField value={Options.laneCover(this.props.options)} onChange={this.props.onSetLaneCover} style={{ width: '5em' }} /> <div className="OptionsPlayerͷhelp" title="Can be negative, in this case the play area is pulled up." > The amount of play area to hide from the top. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="BGA"> <OptionsCheckbox checked={Options.isBackgroundAnimationsEnabled(this.props.options)} onToggle={this.props.onToggleBackgroundAnimationsEnabled} > Enable background animations <span className="OptionsPlayerͷhint">(720p, alpha)</span> </OptionsCheckbox> </OptionsPlayer.Row> <OptionsPlayer.Row label="AutoVel"> <OptionsCheckbox checked={Options.isAutoVelocityEnabled(this.props.options)} onToggle={this.props.onToggleAutoVelocityEnabled} > Maintain absolute note velocity <span className="OptionsPlayerͷhint">(advanced)</span> </OptionsCheckbox> </OptionsPlayer.Row> <div className="OptionsPlayerͷbuttons"> <OptionsButton onClick={this.props.onClose}>Save & Exit</OptionsButton> </div> </div> } })

--- src/app/ui/OptionsPlayer.jsx +++ src/app/ui/OptionsPlayer.jsx @@ -1,176 +1,191 @@ const enhance = compose( connect((state) => ({ options: state.options, scratch: Options.scratchPosition(state.options), })), connectIO({ onSetPanel: () => (value) => OptionsIO.setOptions({ 'player.P1.panel': value }), onSetScratch: () => (position) => OptionsIO.setScratch(position), onSetSpeed: () => (speed) => OptionsIO.setSpeed(speed), onSetLeadTime: () => (leadTime) => OptionsIO.setLeadTime(leadTime), onSetLaneCover: () => (laneCover) => OptionsIO.setLaneCover(laneCover), onToggleBackgroundAnimationsEnabled: ({ options }) => () => ( OptionsIO.setOptions({ 'system.bga.enabled': Options.toggleOption(options['system.bga.enabled']) }) ), onToggleAutoVelocityEnabled: ({ options }) => () => ( OptionsIO.setOptions({ 'player.P1.auto-velocity': Options.toggleOption(options['player.P1.auto-velocity']) }) + ), + onToggleGauge: ({ options }) => () => ( + OptionsIO.setOptions({ + 'player.P1.gauge': Options.toggleGauge(options['player.P1.gauge']) + }) ) }), pure ) export const OptionsPlayer = React.createClass({ propTypes: { options: React.PropTypes.object, scratch: React.PropTypes.string, onClose: React.PropTypes.func, onSetPanel: React.PropTypes.func, onSetScratch: React.PropTypes.func, onSetSpeed: React.PropTypes.func, onSetLaneCover: React.PropTypes.func, onToggleBackgroundAnimationsEnabled: React.PropTypes.func, onToggleAutoVelocityEnabled: React.PropTypes.func, onSetLeadTime: React.PropTypes.func }, render () { return <div className="OptionsPlayer"> <OptionsPlayer.Row label="Speed" hidden={Options.isAutoVelocityEnabled(this.props.options)} > <OptionsSpeed value={this.props.options['player.P1.speed']} onChange={this.props.onSetSpeed} /> <div className="OptionsPlayerͷhelp"> You can also change the speed in-game<br />using the Up and Down arrow keys. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="LeadTime" hidden={!Options.isAutoVelocityEnabled(this.props.options)} > <OptionsLeadTimeInputField value={Options.leadTime(this.props.options)} onChange={this.props.onSetLeadTime} style={{ width: '5em' }} /> <div className="OptionsPlayerͷhelp"> Speed will be automatically adjusted<br />to maintain a consistent note velocity. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="Scratch"> <OptionsPlayerSelector type="scratch" options={SCRATCH_OPTIONS} onSelect={this.props.onSetScratch} value={this.props.scratch} /> </OptionsPlayer.Row> <OptionsPlayer.Row label="Panel"> <OptionsPlayerSelector type="panel" options={PANEL_OPTIONS} onSelect={this.props.onSetPanel} value={this.props.options['player.P1.panel']} /> </OptionsPlayer.Row> <OptionsPlayer.Row label="Cover"> <OptionsLaneCoverInputField value={Options.laneCover(this.props.options)} onChange={this.props.onSetLaneCover} style={{ width: '5em' }} /> <div className="OptionsPlayerͷhelp" title="Can be negative, in this case the play area is pulled up." > The amount of play area to hide from the top. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="BGA"> <OptionsCheckbox checked={Options.isBackgroundAnimationsEnabled(this.props.options)} onToggle={this.props.onToggleBackgroundAnimationsEnabled} > Enable background animations <span className="OptionsPlayerͷhint">(720p, alpha)</span> </OptionsCheckbox> </OptionsPlayer.Row> <OptionsPlayer.Row label="AutoVel"> <OptionsCheckbox checked={Options.isAutoVelocityEnabled(this.props.options)} onToggle={this.props.onToggleAutoVelocityEnabled} > Maintain absolute note velocity <span className="OptionsPlayerͷhint">(advanced)</span> </OptionsCheckbox> </OptionsPlayer.Row> <div className="OptionsPlayerͷbuttons"> <OptionsButton onClick={this.props.onClose}>Save & Exit</OptionsButton> </div> </div> } })

--- src/app/ui/OptionsPlayer.jsx +++ src/app/ui/OptionsPlayer.jsx @@ -1,176 +1,191 @@ const enhance = compose( connect((state) => ({ options: state.options, scratch: Options.scratchPosition(state.options), })), connectIO({ onSetPanel: () => (value) => OptionsIO.setOptions({ 'player.P1.panel': value }), onSetScratch: () => (position) => OptionsIO.setScratch(position), onSetSpeed: () => (speed) => OptionsIO.setSpeed(speed), onSetLeadTime: () => (leadTime) => OptionsIO.setLeadTime(leadTime), onSetLaneCover: () => (laneCover) => OptionsIO.setLaneCover(laneCover), onToggleBackgroundAnimationsEnabled: ({ options }) => () => ( OptionsIO.setOptions({ 'system.bga.enabled': Options.toggleOption(options['system.bga.enabled']) }) ), onToggleAutoVelocityEnabled: ({ options }) => () => ( OptionsIO.setOptions({ 'player.P1.auto-velocity': Options.toggleOption(options['player.P1.auto-velocity']) }) + ), + onToggleGauge: ({ options }) => () => ( + OptionsIO.setOptions({ + 'player.P1.gauge': Options.toggleGauge(options['player.P1.gauge']) + }) ) }), pure ) export const OptionsPlayer = React.createClass({ propTypes: { options: React.PropTypes.object, scratch: React.PropTypes.string, onClose: React.PropTypes.func, onSetPanel: React.PropTypes.func, onSetScratch: React.PropTypes.func, onSetSpeed: React.PropTypes.func, onSetLaneCover: React.PropTypes.func, onToggleBackgroundAnimationsEnabled: React.PropTypes.func, onToggleAutoVelocityEnabled: React.PropTypes.func, + onToggleGauge: React.PropTypes.func, onSetLeadTime: React.PropTypes.func }, render () { return <div className="OptionsPlayer"> <OptionsPlayer.Row label="Speed" hidden={Options.isAutoVelocityEnabled(this.props.options)} > <OptionsSpeed value={this.props.options['player.P1.speed']} onChange={this.props.onSetSpeed} /> <div className="OptionsPlayerͷhelp"> You can also change the speed in-game<br />using the Up and Down arrow keys. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="LeadTime" hidden={!Options.isAutoVelocityEnabled(this.props.options)} > <OptionsLeadTimeInputField value={Options.leadTime(this.props.options)} onChange={this.props.onSetLeadTime} style={{ width: '5em' }} /> <div className="OptionsPlayerͷhelp"> Speed will be automatically adjusted<br />to maintain a consistent note velocity. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="Scratch"> <OptionsPlayerSelector type="scratch" options={SCRATCH_OPTIONS} onSelect={this.props.onSetScratch} value={this.props.scratch} /> </OptionsPlayer.Row> <OptionsPlayer.Row label="Panel"> <OptionsPlayerSelector type="panel" options={PANEL_OPTIONS} onSelect={this.props.onSetPanel} value={this.props.options['player.P1.panel']} /> </OptionsPlayer.Row> <OptionsPlayer.Row label="Cover"> <OptionsLaneCoverInputField value={Options.laneCover(this.props.options)} onChange={this.props.onSetLaneCover} style={{ width: '5em' }} /> <div className="OptionsPlayerͷhelp" title="Can be negative, in this case the play area is pulled up." > The amount of play area to hide from the top. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="BGA"> <OptionsCheckbox checked={Options.isBackgroundAnimationsEnabled(this.props.options)} onToggle={this.props.onToggleBackgroundAnimationsEnabled} > Enable background animations <span className="OptionsPlayerͷhint">(720p, alpha)</span> </OptionsCheckbox> </OptionsPlayer.Row> <OptionsPlayer.Row label="AutoVel"> <OptionsCheckbox checked={Options.isAutoVelocityEnabled(this.props.options)} onToggle={this.props.onToggleAutoVelocityEnabled} > Maintain absolute note velocity <span className="OptionsPlayerͷhint">(advanced)</span> </OptionsCheckbox> </OptionsPlayer.Row> <div className="OptionsPlayerͷbuttons"> <OptionsButton onClick={this.props.onClose}>Save & Exit</OptionsButton> </div> </div> } })

--- src/app/ui/OptionsPlayer.jsx +++ src/app/ui/OptionsPlayer.jsx @@ -1,176 +1,191 @@ const enhance = compose( connect((state) => ({ options: state.options, scratch: Options.scratchPosition(state.options), })), connectIO({ onSetPanel: () => (value) => OptionsIO.setOptions({ 'player.P1.panel': value }), onSetScratch: () => (position) => OptionsIO.setScratch(position), onSetSpeed: () => (speed) => OptionsIO.setSpeed(speed), onSetLeadTime: () => (leadTime) => OptionsIO.setLeadTime(leadTime), onSetLaneCover: () => (laneCover) => OptionsIO.setLaneCover(laneCover), onToggleBackgroundAnimationsEnabled: ({ options }) => () => ( OptionsIO.setOptions({ 'system.bga.enabled': Options.toggleOption(options['system.bga.enabled']) }) ), onToggleAutoVelocityEnabled: ({ options }) => () => ( OptionsIO.setOptions({ 'player.P1.auto-velocity': Options.toggleOption(options['player.P1.auto-velocity']) }) + ), + onToggleGauge: ({ options }) => () => ( + OptionsIO.setOptions({ + 'player.P1.gauge': Options.toggleGauge(options['player.P1.gauge']) + }) ) }), pure ) export const OptionsPlayer = React.createClass({ propTypes: { options: React.PropTypes.object, scratch: React.PropTypes.string, onClose: React.PropTypes.func, onSetPanel: React.PropTypes.func, onSetScratch: React.PropTypes.func, onSetSpeed: React.PropTypes.func, onSetLaneCover: React.PropTypes.func, onToggleBackgroundAnimationsEnabled: React.PropTypes.func, onToggleAutoVelocityEnabled: React.PropTypes.func, + onToggleGauge: React.PropTypes.func, onSetLeadTime: React.PropTypes.func }, render () { return <div className="OptionsPlayer"> <OptionsPlayer.Row label="Speed" hidden={Options.isAutoVelocityEnabled(this.props.options)} > <OptionsSpeed value={this.props.options['player.P1.speed']} onChange={this.props.onSetSpeed} /> <div className="OptionsPlayerͷhelp"> You can also change the speed in-game<br />using the Up and Down arrow keys. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="LeadTime" hidden={!Options.isAutoVelocityEnabled(this.props.options)} > <OptionsLeadTimeInputField value={Options.leadTime(this.props.options)} onChange={this.props.onSetLeadTime} style={{ width: '5em' }} /> <div className="OptionsPlayerͷhelp"> Speed will be automatically adjusted<br />to maintain a consistent note velocity. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="Scratch"> <OptionsPlayerSelector type="scratch" options={SCRATCH_OPTIONS} onSelect={this.props.onSetScratch} value={this.props.scratch} /> </OptionsPlayer.Row> <OptionsPlayer.Row label="Panel"> <OptionsPlayerSelector type="panel" options={PANEL_OPTIONS} onSelect={this.props.onSetPanel} value={this.props.options['player.P1.panel']} /> </OptionsPlayer.Row> <OptionsPlayer.Row label="Cover"> <OptionsLaneCoverInputField value={Options.laneCover(this.props.options)} onChange={this.props.onSetLaneCover} style={{ width: '5em' }} /> <div className="OptionsPlayerͷhelp" title="Can be negative, in this case the play area is pulled up." > The amount of play area to hide from the top. </div> </OptionsPlayer.Row> <OptionsPlayer.Row label="BGA"> <OptionsCheckbox checked={Options.isBackgroundAnimationsEnabled(this.props.options)} onToggle={this.props.onToggleBackgroundAnimationsEnabled} > Enable background animations <span className="OptionsPlayerͷhint">(720p, alpha)</span> </OptionsCheckbox> </OptionsPlayer.Row> <OptionsPlayer.Row label="AutoVel"> <OptionsCheckbox checked={Options.isAutoVelocityEnabled(this.props.options)} onToggle={this.props.onToggleAutoVelocityEnabled} > Maintain absolute note velocity <span className="OptionsPlayerͷhint">(advanced)</span> </OptionsCheckbox> </OptionsPlayer.Row> + <OptionsPlayer.Row label="Gauge"> + <OptionsCheckbox + checked={Options.isGaugeEnabled(this.props.options)} + onToggle={this.props.onToggleGauge} + > + Show expert gauge <span className="OptionsPlayerͷhint">(experimental)</span> + </OptionsCheckbox> + </OptionsPlayer.Row> + <div className="OptionsPlayerͷbuttons"> <OptionsButton onClick={this.props.onClose}>Save & Exit</OptionsButton> </div> </div> } })

Slide № 192 Cohesion loss Symptom: Making a simple change
requires changing code that is further apart.

Slide № 193 Cohesion loss Symptom: Reviewing a PR requires
a lot of scrolling up and down to understand.

Slide № 194 components/ scoreboard/ ScoreboardView.js modules/ constants.js scoreboard/ actions.js
reducer.js selectors.js utils.js

Slide № 195

Slide № 196 200 files 200 files 200 files 500
files

Slide № 197 Let’s try aiming for functional cohesion instead
of logical cohesion.

currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout, onViewMessages: MessagesIO.viewMessages } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func

currentUser: selectCurrentUser(state), newNotificationCount: selectNewNotificationCount(state), newMessageCount: selectNewMessageCount(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout, onViewMessages: MessagesIO.viewMessages } ) class Navigation extends Component { static propTypes = { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func Remove stuff not directly related to Navigation

= { currentUser: PropTypes.object, onLogin: PropTypes.func, onLogout: PropTypes.func, newNotificationCount: PropTypes.number, newMessageCount: PropTypes.number, onViewMessages: PropTypes.func } render () { const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem>

{ const loggedIn = !!this.props.currentUser return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> {loggedIn && <NavItem href='/notifications'> Notifications ({this.props.newNotificationCount}) </NavItem> } {loggedIn && <NavItem href='/inbox' onClick={this.props.onViewMessages}>

{ return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> <NotificationsNavItem /> <MessagesNavItem />

{ return ( <Navbar> <Navbar.Header> <Navbar.Brand> <a href='#'>My app</a> </Navbar.Brand> </Navbar.Header> <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem> <NotificationsNavItem /> <MessagesNavItem /> </Nav> <Nav pullRight> <LoginLogoutNavItem /> </Nav> </Navbar> )

Slide № 209 const LoginLogoutNavItem =

Slide № 210 const LoginLogoutNavItem = connect( )

Slide № 211 const LoginLogoutNavItem = connect( state => ({
currentUser: selectCurrentUser(state) }), )

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function LoginLogoutNavItem (props) { return ( props.currentUser ? ( <NavItem href='#' onClick={props.onLogout}>Logout</NavItem> ) : ( <NavItem href='#' onClick={props.onLogin}>Login</NavItem> ) ) })

Slide № 215 User Navigation Navigation const LoginLogoutNavItem = connect(
state => ({ currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function LoginLogoutNavItem (props) { return ( props.currentUser ? ( <NavItem href='#' onClick={props.onLogout}>Logout</NavItem> ) : ( <NavItem href='#' onClick={props.onLogin}>Login</NavItem> ) ) })

state => ({ currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function LoginLogoutNavItem (props) { return ( props.currentUser ? ( <NavItem href='#' onClick={props.onLogout}>Logout</NavItem> ) : ( <NavItem href='#' onClick={props.onLogin}>Login</NavItem> ) ) }) Delegate rendering logic

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function LoginLogoutNavItem (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) })

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function LoginLogoutNavItem (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) LoginLogoutNavItem.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired }

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function LoginLogoutNavItem (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) LoginLogoutNavItem.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired } User Only concerned about current user and authentication Not concerned about how to render it

Slide № 227 User const LoginLogoutNavItem = connect( state =>
({ currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function LoginLogoutNavItem (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) LoginLogoutNavItem.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired }

Slide № 228 User const Auth = connect( state =>
({ currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function Auth (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired }

Slide № 229 const Auth = connect( state => ({
currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function Auth (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired }

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function Auth (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired } “Render props”

Slide № 231 Back to our <Navigation />

Slide № 233 <Nav> <NavItem href='/'>Home</NavItem> <NavItem href='/explore'>Explore</NavItem> <NavItem href='/search'>Search</NavItem>
<NotificationsNavItem /> <MessagesNavItem /> </Nav> <Nav pullRight> <LoginLogoutNavItem /> </Nav> </Navbar> ) } }

<NotificationsNavItem /> <MessagesNavItem /> </Nav> <Nav pullRight> <LoginLogoutNavItem /> </Nav> </Navbar> ) } }

<NotificationsNavItem /> <MessagesNavItem /> </Nav> <Nav pullRight> <Auth /> </Nav> </Navbar> ) } } Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired }

<NotificationsNavItem /> <MessagesNavItem /> </Nav> <Nav pullRight> <Auth renderLoggedOut={ } renderLoggedIn={ } /> </Nav> </Navbar> ) } } Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired }

<NotificationsNavItem /> <MessagesNavItem /> </Nav> <Nav pullRight> <Auth renderLoggedOut={(login) => <NavItem href='#' onClick={login}>Login</NavItem> } renderLoggedIn={(user, logout) => <NavItem href='#' onClick={logout}>Logout</NavItem> } /> </Nav> </Navbar> ) } } Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired }

Slide № 239 <Auth />

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function Auth (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired }

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function Auth (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired } Objective: Connect UI to data source.

currentUser: selectCurrentUser(state) }), { onLogin: LoginIO.showLoginModal, onLogout: LoginIO.logout } )(function Auth (props) { return ( props.currentUser ? ( props.renderLoggedIn(props.currentUser, props.onLogout) ) : ( props.renderLoggedOut(props.onLogin) ) ) }) Auth.propTypes = { renderLoggedIn: PropTypes.func.isRequired, renderLoggedOut: PropTypes.func.isRequired } “Data connector component”

Slide № 243 Navigation

Slide № 244 Navigation

Slide № 245 NavigationContainer NavigationView

Slide № 246 Navigation Auth Unread MessagesData Unread NotificationsData

Slide № 247 Navigation Auth Unread MessagesData Unread NotificationsData

Slide № 248 Conclusions

Slide № 249 When code reviewing Consistency Readability Logical correctness

Slide № 250 When code reviewing Consistency Readability Logical correctness
Smells

Slide № 251 I don’t know of any way to
detect these smells automatically.

Slide № 252 When writing/reviewing code, try looking for these
smells.

Slide № 253 Not all smells are bad.

Slide № 254 Not all smells are bad. Example: Duplicated
code

Slide № 255 Not all smells are bad. Example: Duplicated
code can sometimes be easier to read

Slide № 256

Slide № 257 Everything is a trade-off.

Slide № 258 Look for feedback.

Slide № 259 Thank you!

Smells in React Apps

Smells in React Apps

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