callbacks.ts

const website = `nir.life`

const btn = document.createElement('button');

function map(transformFn) {
  return function(inputValueProvider) {
    return createObservable(
        function (onValue, onError, onComplete) {
          inputValueProvider.subscribe(
              (value) => onValue(transformFn(value)),
              (error) => onError(error),
              () => onComplete()
          )
        }
    )
  }
}
function filter(conditionFn) {
  return function(inputValueProvider) {
    return createObservable(
        function (onValue, onError, onComplete) {
          inputValueProvider.subscribe(
              (value) => conditionFn(value) && onValue(value),
              (error) => onError(error),
              () => onComplete()
          )
        }
    )
  }
}
function tap(callback){}

function createObservable(subscribeFn) {
  return {
    subscribe: subscribeFn,
    pipe: function (operator) {
      return operator(this)
    }
  }
}

const numbers$ = createObservable(
    function getValues(onValue, onError, onComplete) {
      [10, 20, 30].forEach(onValue);
      onComplete()
    }
)


const click$ = createObservable(
    function getValues(onValue, onError, onComplete) {
      btn.addEventListener('click', onValue)
    }
)

// callbacks
function next(value) {
  console.log(value);
}
function error(error) {
  console.log(error);
}
function complete() {
  console.log('Done!')
}

numbers$
    .pipe(map(v => v * 100))
    .pipe(filter(v => v !== 2000))
    .subscribe(next, error, complete)

click$
    .pipe(map(e => ({name: 'event!'})))
    .subscribe(next, error, complete)


btn.dispatchEvent(new Event('click'))