Functional Reactive Programming 

Johnny Austin

@recursivefunk

CodePen DC

1/15/15

About Me

Director of Technoloy

Contributor

Reluctant Proponent

Fanboy! (oh-em-gee)

Agenda

  • Functional Programming
  • Reactive Programming
  • Functional Reactive¬†
    • Demo!

Functional Programming

Functional Programming

  • No clear definition
  • Contrast with OOP
    • OOP composes objects / methods
    • OOP owns it's data and operations
    • FP just uses functions to perform operations
      • Central data structure are functions
      • Function composition
  • Loosely coupled from data
    • Generic operations
      • Data in, data out
      • No side effects

Functional Programming cont.

var bar = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
var foo = bar

    .filter(function(item) {
        return item > 5;
    })
    
    .map(function(item) {
        return item * 2;
    }); 

log( foo ); // [ 12, 14, 16, 18, 20 ]
log( bar ); // [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]

Reactive Programming

Reactive Programming

  • Programming around data streams
  • Streams
    • Data over time
    • Old Concept
      • Events¬†
        • document.addEventListener
        • $('#foo').on('click')
      • Node.js (io.js? hehe) Streams
      • Pub/Sub
    • Signals
  • More efficient than polling
  • Easier to understand

Reactive Programming cont.

// the dom ---------------------------------
$('#text-input').on('click', function(e){
  var entered = e.target.value;
  $('#output').html( entered );
});


// the server ------------------------------
fs
  .createReadStream( './some/file.txt' )
  .on('data', function(){
    // do something with the data  
  })
  .on('error', function(){
    // :(
  })
  .pipe( anotherStream );


// socket.io --------------------------------
io.sockets.on('connection', function (socket) {
  var payload = {
    msg: 'all your events are belong to us'
  };
  socket.broadcast.emit( 'readMe', payload );
});

Reactive Programming cont.

  • Bigger than code
    • System architecture
      • Non-monolithic
      • Distributed

Functional

  • Non OO
  • Single concern
  • No side effects
    • Immutability

Reactive

  • Streams of data over time
  • Events/PubSub etc
  • Signals (error, complete)

Review (so far)

Functional Reactive Programming

DEMO

github.com/jray/tiny-frp

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By Johnny Ray Austin

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