eggheadio-projects/getting-to-know-the-state-monad-in-javascript: null

(function(root) {
  
  const compose =
    (f, g) => x => f(g(x))
  
  root.helpers = {
    compose
  }
})(window)

<!DOCTYPE html>
<html>

  <head>
    <script data-require="crocks@*" data-semver="0.8.1" src="https://unpkg.com/crocks@0.8.1/dist/crocks.min.js"></script>
    <link rel="stylesheet" href="style.css" />
  </head>

  <body>
    <script src="logger.js"></script>
    <script src="script.js"></script>
  </body>

</html>

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  globalName:"log",
  root:window,
  selector:"body",
  fontSize:"28px",
  colors: {
    background:"transparent",
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    label:"blue",
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    number:"violet",
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});

const { State } = crocks
const { Pair } = crocks


// State s a
// (s -> Pair(a, s))
// m :: State Number String

const m =
  State(state => Pair('value', state))

log('State instance', m)

log(
  'Running',
  m.runWith(45)
)

log(
  'pull value (fst)',
  m.runWith(45).fst()
)

log(
  'pull state (snd)',
  m.runWith(45).snd()
)

const resultant =
  State(state => Pair(state + 5, state))

log(
  'resultant (fst)',
  resultant.runWith(45).fst()
)

const state =
  State(state => Pair(state, state + 5))

log(
  'state (snd)',
  state.runWith(45).snd()
)

// updateValue :: Number -> State Number
const updateValue = x =>
  State(s => Pair(s + x, s))

log(
  'updateValue',
  updateValue(10)
    .runWith(45)
)

// updateState :: Number -> State Number
const updateState = x =>
  State(s => Pair(s, s + x))

log(
  'updateState',
  updateState(10)
    .runWith(45)
)