app-2.ts

import { Action } from "./ngrx-falso/ngrx";
import { incrementadorAction, decrementadorAction, multiplicarAction, dividirAction, resetearAction } from "./contador/contador.actions"

function reducer(state = 10, action: Action) {
    switch (action.type) {
        case 'INCREMENTAR':
            return state += 1;

        case 'DECREMENTAR':
            return state -= 1;

        case 'MULTIPLICAR':
            return state * action.payload;

        case 'DIVIDIR':
            return state / action.payload;

        case 'RESETEAR':
            return state = 0;

        default:
            return state;
    }
}

console.log(reducer(10, incrementadorAction));
console.log(reducer(10, decrementadorAction));
console.log(reducer(10, multiplicarAction));
console.log(reducer(10, dividirAction));
console.log(reducer(10, resetearAction));