(function (global, factory) {
    typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
    typeof define === 'function' && define.amd ? define(['exports'], factory) :
    (global = global || self, factory(global.Redux = {}));
    }(this, function (exports) { 'use strict';
    
    function symbolObservablePonyfill(root) {
        var result;
        var Symbol = root.Symbol;
    
        if (typeof Symbol === 'function') {
            if (Symbol.observable) {
                result = Symbol.observable;
            } else {
                result = Symbol('observable');
                Symbol.observable = result;
            }
        } else {
            result = '@@observable';
        }
    
        return result;
    }
    
    /* global window */
    
    var root;
    
    if (typeof self !== 'undefined') {
      root = self;
    } else if (typeof window !== 'undefined') {
      root = window;
    } else if (typeof global !== 'undefined') {
      root = global;
    } else if (typeof module !== 'undefined') {
      root = module;
    } else {
      root = Function('return this')();
    }
    
    var result = symbolObservablePonyfill(root);
    
    //创建一个随机字符串
    var randomString = function randomString() {
      return Math.random().toString(36).substring(7).split('').join('.');
    };
    
    var ActionTypes = {
      INIT: "@@redux/INIT" + randomString(),
      REPLACE: "@@redux/REPLACE" + randomString(),
      PROBE_UNKNOWN_ACTION: function PROBE_UNKNOWN_ACTION() {
        return "@@redux/PROBE_UNKNOWN_ACTION" + randomString();
      }
    };
    
    //是否为原生对象，原生对象是指new Object()或者{}类型的对象
    function isPlainObject(obj) {
      if (typeof obj !== 'object' || obj === null) return false;
      var proto = obj;
    
      while (Object.getPrototypeOf(proto) !== null) {
        proto = Object.getPrototypeOf(proto);
      }
    
      return Object.getPrototypeOf(obj) === proto;
    }
    
    //创建一个store用于管理状态树，当有多个reducer时，需要组合成一个reducer
    function createStore(reducer, preloadedState, enhancer) {
      var _ref2;
    
      if (typeof preloadedState === 'function' && typeof enhancer === 'function' || typeof enhancer === 'function' && typeof arguments[3] === 'function') {
        throw new Error('It looks like you are passing several store enhancers to ' + 'createStore(). This is not supported. Instead, compose them ' + 'together to a single function.');
      }
    
      if (typeof preloadedState === 'function' && typeof enhancer === 'undefined') {
        enhancer = preloadedState;
        preloadedState = undefined;
      }
    
      if (typeof enhancer !== 'undefined') {
        if (typeof enhancer !== 'function') {
          throw new Error('Expected the enhancer to be a function.');
        }
    
        return enhancer(createStore)(reducer, preloadedState);
      }
    
      if (typeof reducer !== 'function') {
        throw new Error('Expected the reducer to be a function.');
      }
    
      var currentReducer = reducer;
      var currentState = preloadedState;
      var currentListeners = [];
      var nextListeners = currentListeners;
      var isDispatching = false;
      //复制一个数组，用于保存下一个监听函数
      function ensureCanMutateNextListeners() {
        if (nextListeners === currentListeners) {
          nextListeners = currentListeners.slice();
        }
      }
      //获取当前状态
      function getState() {
        if (isDispatching) {
          throw new Error('You may not call store.getState() while the reducer is executing. ' + 'The reducer has already received the state as an argument. ' + 'Pass it down from the top reducer instead of reading it from the store.');
        }
    
        return currentState;
      }
      /**
       * 添加监听函数，当状态改变时，可以通知到view进行更新
       */
    
    
      function subscribe(listener) {
        if (typeof listener !== 'function') {
          throw new Error('Expected the listener to be a function.');
        }
    
        if (isDispatching) {
          throw new Error('You may not call store.subscribe() while the reducer is executing. ' + 'If you would like to be notified after the store has been updated, subscribe from a ' + 'component and invoke store.getState() in the callback to access the latest state. ' + 'See https://redux.js.org/api-reference/store#subscribelistener for more details.');
        }
    
        var isSubscribed = true;
        //复制nextListeners
        ensureCanMutateNextListeners();
        //添加监听函数
        nextListeners.push(listener);
        //使用一个闭包，保存listener的作用域，当执行该函数时，可以将listener从监听器数组中移除
        return function unsubscribe() {
          if (!isSubscribed) {
            return;
          }
    
          if (isDispatching) {
            throw new Error('You may not unsubscribe from a store listener while the reducer is executing. ' + 'See https://redux.js.org/api-reference/store#subscribelistener for more details.');
          }
    
          isSubscribed = false;
          ensureCanMutateNextListeners();
          var index = nextListeners.indexOf(listener);
          nextListeners.splice(index, 1);
          currentListeners = null;
        };
      }
      /**
       * 调用action
       */
      function dispatch(action) {
        if (!isPlainObject(action)) {
          throw new Error('Actions must be plain objects. ' + 'Use custom middleware for async actions.');
        }
    
        if (typeof action.type === 'undefined') {
          throw new Error('Actions may not have an undefined "type" property. ' + 'Have you misspelled a constant?');
        }
    
        if (isDispatching) {
          throw new Error('Reducers may not dispatch actions.');
        }
    
        try {
          isDispatching = true;
          //获取当前状态
          currentState = currentReducer(currentState, action);
        } finally {
          isDispatching = false;
        }
    
        var listeners = currentListeners = nextListeners;
        //执行每一个监听函数
        for (var i = 0; i < listeners.length; i++) {
          var listener = listeners[i];
          listener();
        }
    
        return action;
      }
      //替换reducer函数
      function replaceReducer(nextReducer) {
        if (typeof nextReducer !== 'function') {
          throw new Error('Expected the nextReducer to be a function.');
        }
    
        currentReducer = nextReducer;
        dispatch({
          type: ActionTypes.REPLACE
        });
      }
      function observable() {
        var _ref;
    
        var outerSubscribe = subscribe;
        return _ref = {
          subscribe: function subscribe(observer) {
            if (typeof observer !== 'object' || observer === null) {
              throw new TypeError('Expected the observer to be an object.');
            }
    
            function observeState() {
              if (observer.next) {
                observer.next(getState());
              }
            }
    
            observeState();
            var unsubscribe = outerSubscribe(observeState);
            return {
              unsubscribe: unsubscribe
            };
          }
        }, _ref[result] = function () {
          return this;
        }, _ref;
      } 
    
      //创建初始状态
      dispatch({
        type: ActionTypes.INIT
      });
      return _ref2 = {
        dispatch: dispatch,
        subscribe: subscribe,
        getState: getState,
        replaceReducer: replaceReducer
      }, _ref2[result] = observable, _ref2;
    }
    
    //错误处理
    function warning(message) {
      if (typeof console !== 'undefined' && typeof console.error === 'function') {
        console.error(message);
      }
    
    
      try {
        throw new Error(message);
      } catch (e) {} 
    
    }
    
    function getUndefinedStateErrorMessage(key, action) {
      var actionType = action && action.type;
      var actionDescription = actionType && "action \"" + String(actionType) + "\"" || 'an action';
      return "Given " + actionDescription + ", reducer \"" + key + "\" returned undefined. " + "To ignore an action, you must explicitly return the previous state. " + "If you want this reducer to hold no value, you can return null instead of undefined.";
    }
    
    function getUnexpectedStateShapeWarningMessage(inputState, reducers, action, unexpectedKeyCache) {
      var reducerKeys = Object.keys(reducers);
      var argumentName = action && action.type === ActionTypes.INIT ? 'preloadedState argument passed to createStore' : 'previous state received by the reducer';
    
      if (reducerKeys.length === 0) {
        return 'Store does not have a valid reducer. Make sure the argument passed ' + 'to combineReducers is an object whose values are reducers.';
      }
    
      if (!isPlainObject(inputState)) {
        return "The " + argumentName + " has unexpected type of \"" + {}.toString.call(inputState).match(/\s([a-z|A-Z]+)/)[1] + "\". Expected argument to be an object with the following " + ("keys: \"" + reducerKeys.join('", "') + "\"");
      }
    
      var unexpectedKeys = Object.keys(inputState).filter(function (key) {
        return !reducers.hasOwnProperty(key) && !unexpectedKeyCache[key];
      });
      unexpectedKeys.forEach(function (key) {
        unexpectedKeyCache[key] = true;
      });
      if (action && action.type === ActionTypes.REPLACE) return;
    
      if (unexpectedKeys.length > 0) {
        return "Unexpected " + (unexpectedKeys.length > 1 ? 'keys' : 'key') + " " + ("\"" + unexpectedKeys.join('", "') + "\" found in " + argumentName + ". ") + "Expected to find one of the known reducer keys instead: " + ("\"" + reducerKeys.join('", "') + "\". Unexpected keys will be ignored.");
      }
    }
    
    //初始化状态
    function assertReducerShape(reducers) {
      Object.keys(reducers).forEach(function (key) {
        var reducer = reducers[key];
        var initialState = reducer(undefined, {
          type: ActionTypes.INIT
        });
    
        if (typeof initialState === 'undefined') {
          throw new Error("Reducer \"" + key + "\" returned undefined during initialization. " + "If the state passed to the reducer is undefined, you must " + "explicitly return the initial state. The initial state may " + "not be undefined. If you don't want to set a value for this reducer, " + "you can use null instead of undefined.");
        }
    
        if (typeof reducer(undefined, {
          type: ActionTypes.PROBE_UNKNOWN_ACTION()
        }) === 'undefined') {
          throw new Error("Reducer \"" + key + "\" returned undefined when probed with a random type. " + ("Don't try to handle " + ActionTypes.INIT + " or other actions in \"redux/*\" ") + "namespace. They are considered private. Instead, you must return the " + "current state for any unknown actions, unless it is undefined, " + "in which case you must return the initial state, regardless of the " + "action type. The initial state may not be undefined, but can be null.");
        }
      });
    }
    
    
    // 合并reducers
    function combineReducers(reducers) {
      var reducerKeys = Object.keys(reducers);
      var finalReducers = {};
    
      for (var i = 0; i < reducerKeys.length; i++) {
        var key = reducerKeys[i];
    
        {
          if (typeof reducers[key] === 'undefined') {
            warning("No reducer provided for key \"" + key + "\"");
          }
        }
    
        if (typeof reducers[key] === 'function') {
          finalReducers[key] = reducers[key];
        }
      }
    
      var finalReducerKeys = Object.keys(finalReducers); 
    
      var unexpectedKeyCache;
    
      {
        unexpectedKeyCache = {};
      }
    
      var shapeAssertionError;
    
      try {
        assertReducerShape(finalReducers);
      } catch (e) {
        shapeAssertionError = e;
      }
    
      return function combination(state, action) {
        if (state === void 0) {
          state = {};
        }
    
        if (shapeAssertionError) {
          throw shapeAssertionError;
        }
    
        {
          var warningMessage = getUnexpectedStateShapeWarningMessage(state, finalReducers, action, unexpectedKeyCache);
    
          if (warningMessage) {
            warning(warningMessage);
          }
        }
    
        var hasChanged = false;
        var nextState = {};
    
        for (var _i = 0; _i < finalReducerKeys.length; _i++) {
          var _key = finalReducerKeys[_i];
          var reducer = finalReducers[_key];
          var previousStateForKey = state[_key];
          var nextStateForKey = reducer(previousStateForKey, action);
    
          if (typeof nextStateForKey === 'undefined') {
            var errorMessage = getUndefinedStateErrorMessage(_key, action);
            throw new Error(errorMessage);
          }
    
          nextState[_key] = nextStateForKey;
          hasChanged = hasChanged || nextStateForKey !== previousStateForKey;
        }
    
        hasChanged = hasChanged || finalReducerKeys.length !== Object.keys(state).length;
        return hasChanged ? nextState : state;
      };
    }
    
    function bindActionCreator(actionCreator, dispatch) {
      return function () {
        return dispatch(actionCreator.apply(this, arguments));
      };
    }
  
    
    function bindActionCreators(actionCreators, dispatch) {
      if (typeof actionCreators === 'function') {
        return bindActionCreator(actionCreators, dispatch);
      }
    
      if (typeof actionCreators !== 'object' || actionCreators === null) {
        throw new Error("bindActionCreators expected an object or a function, instead received " + (actionCreators === null ? 'null' : typeof actionCreators) + ". " + "Did you write \"import ActionCreators from\" instead of \"import * as ActionCreators from\"?");
      }
    
      var boundActionCreators = {};
    
      for (var key in actionCreators) {
        var actionCreator = actionCreators[key];
    
        if (typeof actionCreator === 'function') {
          boundActionCreators[key] = bindActionCreator(actionCreator, dispatch);
        }
      }
    
      return boundActionCreators;
    }
    
    function _defineProperty(obj, key, value) {
      if (key in obj) {
        Object.defineProperty(obj, key, {
          value: value,
          enumerable: true,
          configurable: true,
          writable: true
        });
      } else {
        obj[key] = value;
      }
    
      return obj;
    }
    
    function ownKeys(object, enumerableOnly) {
      var keys = Object.keys(object);
    
      if (Object.getOwnPropertySymbols) {
        keys.push.apply(keys, Object.getOwnPropertySymbols(object));
      }
    
      if (enumerableOnly) keys = keys.filter(function (sym) {
        return Object.getOwnPropertyDescriptor(object, sym).enumerable;
      });
      return keys;
    }
    
    function _objectSpread2(target) {
      for (var i = 1; i < arguments.length; i++) {
        var source = arguments[i] != null ? arguments[i] : {};
    
        if (i % 2) {
          ownKeys(source, true).forEach(function (key) {
            _defineProperty(target, key, source[key]);
          });
        } else if (Object.getOwnPropertyDescriptors) {
          Object.defineProperties(target, Object.getOwnPropertyDescriptors(source));
        } else {
          ownKeys(source).forEach(function (key) {
            Object.defineProperty(target, key, Object.getOwnPropertyDescriptor(source, key));
          });
        }
      }
    
      return target;
    }
    
    // 组合reducer
    function compose() {
      for (var _len = arguments.length, funcs = new Array(_len), _key = 0; _key < _len; _key++) {
        funcs[_key] = arguments[_key];
      }
    
      if (funcs.length === 0) {
        return function (arg) {//纯函数
          return arg;
        };
      }
    
      if (funcs.length === 1) {//返回第一个
        return funcs[0];
      }
    
      return funcs.reduce(function (a, b) {//合并
        return function () {
          return a(b.apply(void 0, arguments));
        };
      });
    }
    
    //使用中间件
    function applyMiddleware() {
      for (var _len = arguments.length, middlewares = new Array(_len), _key = 0; _key < _len; _key++) {
        middlewares[_key] = arguments[_key];
      }
    
      return function (createStore) {
        return function () {
          var store = createStore.apply(void 0, arguments);
    
          var _dispatch = function dispatch() {
            throw new Error('Dispatching while constructing your middleware is not allowed. ' + 'Other middleware would not be applied to this dispatch.');
          };
    
          var middlewareAPI = {
            getState: store.getState,
            dispatch: function dispatch() {
              return _dispatch.apply(void 0, arguments);
            }
          };
          var chain = middlewares.map(function (middleware) {
            return middleware(middlewareAPI);
          });
          _dispatch = compose.apply(void 0, chain)(store.dispatch);
          return _objectSpread2({}, store, {
            dispatch: _dispatch
          });
        };
      };
    }
    
  
    
    function isCrushed() {}
    
    if ( typeof isCrushed.name === 'string' && isCrushed.name !== 'isCrushed') {
      warning('You are currently using minified code outside of NODE_ENV === "production". ' + 'This means that you are running a slower development build of Redux. ' + 'You can use loose-envify (https://github.com/zertosh/loose-envify) for browserify ' + 'or setting mode to production in webpack (https://webpack.js.org/concepts/mode/) ' + 'to ensure you have the correct code for your production build.');
    }
    
    exports.__DO_NOT_USE__ActionTypes = ActionTypes;
    exports.applyMiddleware = applyMiddleware;
    exports.bindActionCreators = bindActionCreators;
    exports.combineReducers = combineReducers;
    exports.compose = compose;
    exports.createStore = createStore;
    
    Object.defineProperty(exports, '__esModule', { value: true });
    
    }));