redux.js

var Mocha = require('mocha')
var assert = require('assert')
var _ = require('lodash')
var mocha = new Mocha()
mocha.suite.emit('pre-require', this, 'solution', mocha)


describe('Test suite', function() {
  it('should work', function() {
    assert(true)
  })
  it("can create a store", () => {
    const store = createStore(state => state);
    assert(typeof store.subscribe === "function");
    assert(typeof store.dispatch === "function");
    assert(typeof store.getState === "function");
  });
  it("initializes with initial state", () => {
    const initialState = { foo: true, bar: false };
    const store = createStore((state, action) => state, initialState);
    const state = store.getState();
    assert(Object.keys(state).length === 2);
    assert(state.foo === true);
    assert(state.bar === false);
  });
  it("can dispatch actions", () => {
    const reducer = (state, action) => {
      if (action.type !== "SET_NAME") {
        return state;
      }
      return {
        ...state,
        name: action.payload
      };
    };

    const store = createStore(reducer);
    store.dispatch({ type: "FOO", payload: "bar" });
    assert(store.getState().name === undefined);
    store.dispatch({ type: "SET_NAME", payload: "foo" });
    assert(store.getState().name === "foo");
  });
  it("can subscribe and unsubscribe", () => {
    const reducer = (state, action) => {
      if (action.type !== "SET_NAME") {
        return state;
      }
      return {
        ...state,
        name: action.payload
      };
    };

    const store = createStore(reducer);
    let name = undefined;
    const unsubscribe = store.subscribe(state => {
      name = state.name;
      unsubscribe();
    });
    assert(name === undefined);
    store.dispatch({ type: "SET_NAME", payload: "bar" });
    assert(name === "bar");
    assert(store.getState().name === "bar");

    store.dispatch({ type: "SET_NAME", payload: "baz" });
    assert(name === "bar");
    assert(store.getState().name === "baz");
  });
  it("can have multiple subscribers", () => {
    const store = createStore(state => state);
    let callCount1 = 0;
    let callCount2 = 0;
    let callCount3 = 0;
    store.subscribe(() => {
      callCount1++;
    })
    const unsubscribe = store.subscribe(() => {
      callCount2++;
      unsubscribe();
    })
    store.subscribe(() => { 
      callCount3++;
    })
    store.dispatch({ type: 'foo' });
    assert(callCount1 === 1);
    assert(callCount2 === 1);
    assert(callCount3 === 1);
    store.dispatch({ type: 'foo' });
    assert(callCount1 === 2);
    assert(callCount2 === 1);
    assert(callCount3 === 2);
  });
  it("initializes reducer", () => {
    const initialState = { name: "foo" };

    const reducer = (state = initialState, action) => {
      if (action.type !== "SET_NAME") {
        return state;
      }
      return {
        ...state,
        name: action.payload
      };
    };

    const store = createStore(reducer);
    assert(store.getState().name === "foo");
  });
})


class Store {
  
  constructor (reducer, initialState) {
    this.reducer = reducer;
    this.state = initialState || reducer(undefined, {}) || {};
    this.subscribers = [];
  }
  subscribe(f) {
    this.subscribers.push(f);
    return () => {
      this.subscribers = _.without(this.subscribers, f);
    }
  }
  dispatch(action) {
    let newState = this.reducer(this.state, action);
    this.subscribers.forEach(f => f(newState));
    this.state = newState;
  }
  getState() {
    
    return this.state;
  }
}

function createStore (r, initialState) {
  return new Store(r, initialState);
}


mocha.run()