evgenyfedorenko

function reduceState(stateActionPair = { state: undefined }, [action, reducer]) {
  const { state } = stateActionPair;
  return { state: reducer(state, action), action };
}

evgenyfedorenko

export function select<T, Props, K>(selector: (state: T, props?: Props) => any) {
  return function selectOperator(source$: Observable<T>): Observable<K> {
    let mapped$: Observable<any>;

    mapped$ = source$.pipe(
      map(source => selector(source))
    );

    return mapped$.pipe(distinctUntilChanged());
  };

evgenyfedorenko

export function createSelector(...args: any[]) {
  const selectors = args.slice(0, args.length - 1);
  const projector = args[args.length - 1];

  return function (state: any) {
    const args = selectors.map(fn => fn(state));

    return projector.apply(null, args);
  };
}

evgenyfedorenko

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs';
import * as fromRoot from './reducers/';
import { Increment, Decrement, Reset } from './actions/counter.actions';
import { StoreService, select } from './store.service';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
})