functional & reactive uis with javascript · functional & reactive uis with javascript...
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Functional & Reactive UIs with JavaScript
Lambda Days 2016
Survey
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OOP: Alan KeyObjects communicate by asynchronous message passing
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My story
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2005
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PythonResearch Internship at LIMSI in Paris
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Functional programming
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First-class functionsFunctions as datatype: passed around, returned, etc.
OCamlIntroduction to functional programming by Marc Pouzet
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MLDeveloped in 1970 by Robin Milner
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ML InfluenceHaskell, Elm, …
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UIs
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HCIHuman-Computer Interaction
H C
Model-View-ControllerTrygve Reenskaug in the 1970s
Smalltalk-76At XEROX PARC
MVCDigital model vs Mental model
View
Model
Controller
User
Callback-basedClassical approach
Functional UIs
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ReactGreatly improved rendering engine
DeclarativeSimple and straightforward UI representation
UI is fn of stateFunctional foundation
f(D0) -> V0
f(D1) -> V1
diff(V0, V1) = changes
DOM
Data
Virtual DOM
View
Store
DispatcherActions
User Inputs
Callbacks
Action Creators
New ConceptsDifficult for newcomers
Reactive programming
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A spreadsheetMost popular reactive programming tool
A B
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PassiveB allows others to change its state
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ReactiveB manages its state by reacting to external events
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Separation of concernsA and B are responsible for themselves
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EncapsulationB hides its internals
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ReactiveIndependent, self-contained modules
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Values over timeFirst class concept
ObservableSimple abstraction: Observer + Iterator
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Marble Diagram
Lazy event stream0+ events, finite or infinite
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AsynchronicityDoing more simpler
What, not howDeclarative approach to program logic
Simple compositionOutputs can be given as inputs
UnificationPromises, Callbacks, Web Workers, Web Sockets
RxJSJavaScript reactive programming library
const doubleClickObservable = clickObservable .buffer(() => clickObservable.debounce(250)) .map(arr => arr.length) .filter(x => x === 2);
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Let’s combine
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Cycle.jsFunctional and reactive UI framework in JavaScript
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ConciseBoth the framework and applications built with it
Simple APICycle.run()
fn : input -> outputConstant dialogue
http://cycle.js.org/dialogue.html
computer()fn : inputDevices -> outputDevices
human()fn : senses -> actuators
UIs as « cycles »Natural way for interactions
main()Your application as a pure function
function computer(userEventsObservable) { return userEventsObservable .map(event => /* ... */) .filter(somePredicate) .flatMap(transformItToScreenPixels);}
Sourcesinputs: read effects from the external world
Sinksoutputs: write effects to apply to the external world
DriversPlugins that manage the side effects
Model-View-IntentParts of the main() function
IntentProcessing inputs from the external world
ModelIt represents the state
Viewit creates the output e.g. virtual dom
ComposableDataflow components
Demo
function main() { return { DOM: Rx.Observable.interval(1000) .map(i => CycleDOM.h1('' + i + ' seconds elapsed')) };}
function main(sources) { return { DOM: sources.DOM.select('.field').events('input') .map(ev => ev.target.value) .startWith('') .map(name => div([ input('.field', {attributes: {type: 'text'}}), h1('Hello ' + name), ]) ) };}
FunctionalApplications made of pure functions
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ReactiveObservables simplify events, async & errors handling
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Q? / Thank you
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