dtipson

// Let's make it possible to create pure functions even when we're 
// dealing with impure operations that would have side effects!

// First we'll need a "Type" that can contain a (sometimes impure) function
function IO(fn) {
  if (!(this instanceof IO)) {//make it simpler for end users to create a type without "new"
    return new IO(fn);
  }
  this.runIO = fn;//IO now provides an extra control layer that allows the composition of unexecuted effects

dtipson

function throttle(fn, threshhold = 250, scope) {
  var last,
      deferTimer;
  return function () {
    var context = scope || this;

    var now = +new Date,
        args = arguments;
    if (last && now < last + threshhold) {
      // hold on to it

dtipson

var reduce = fn => (Arr, acc) => Arr.reduce(fn, acc);

var add = reduce((acc,x)=>acc+x);

add([1,2,3],0);// -> 6

dtipson

getUserCommentsbyId = program(
  getUserbyIdAPI, // <-aysnc
  pick('commenterID'), // <-sync
  commentSearchAPI, // <-aysnc
  R.head, // <-sync
  R.tap(console.log.bind(console)) // <-sync, logs result to console
);

// these each return a promise resolved with a user's latest comment based on a userID
getUserCommentsbyId(345);

dtipson

//returns a promise that resolves after a time
function wait(time){
    return new Promise(function(resolve){
      window.setTimeout(resolve,time);
    });
}

//a function that, if called with just a time,
//returns a function that will return a wait...
//that resolves with whatever value it was given

dtipson

const program = (...list) => acc => list.reduce( (acc,fn) => acc.then(fn), Promise.resolve(acc));

dtipson

document.body.innerHTML = '';

const delay = milliseconds => x => new Promise(resolve => setTimeout(resolve, milliseconds, x));

//requestRecord :: Object (optional) -> Promise Stream
const requestRecord = (config={video:true, audio:true}) => {
  return navigator.mediaDevices && navigator.mediaDevices.getUserMedia ?
    navigator.mediaDevices.getUserMedia(config).then(delay(1400)) : // delay avoid startup flash
    Promise.reject('no support for getUserMedia');

dtipson

const program = (...list) => 
                      acc =>
                      R.flatten(list).reduce( (acc,fn) => acc.then(fn), Promise.resolve(acc));

dtipson

// mapping over an array with an async function
// would return an Array of Promises which isn't 
// super useful to work with on its own

async function fooPromise(x){ 
  return Promise.resolve(x*3);
}

const arr = [6,7,8,9];// -> [Promise[18],Promise[21],Promise[24],Promise[27]]]

dtipson

//main function for creating an inline worker:
//inlineWorker:: Function -> a -> Promise b
const inlineWorker = fn => msg =>  {
  const scriptString = `const func = ${fn.toString()}; 
    addEventListener('message', function(e) {
      Promise.resolve(e.data)
        .then(func)
        .then(postMessage);
    }, false);
  `;