函数式编程改用es5写

Question

对函数式编程还是有点懵...下面是redux-logger的源码：

function createLogger(options = {}) {
  /**
   * 传入 applyMiddleWare 的函数
   * @param  {Function} { getState      }) [description]
   * @return {[type]}      [description]
   */
  return ({ getState }) => (next) => (action) => {
    let returnedValue;
    const logEntry = {};
    logEntry.prevState = stateTransformer(getState());
    logEntry.action = action;
    // .... 
    returnedValue = next(action);
    // ....
    logEntry.nextState = stateTransformer(getState());
    // ....
    return returnedValue;
  };
}

可以看到有很多的箭头函数。

其实如果不用箭头函数，用es5的function的方式写出来会是什么样子的呢？

Answer 1

function createLogger() {
  var options = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};

  /**
   * 传入 applyMiddleWare 的函数
   * @param  {Function} { getState      }) [description]
   * @return {[type]}      [description]
   */
  return function (_ref) {
    var getState = _ref.getState;
    return function (next) {
      return function (action) {
        var returnedValue = void 0;
        var logEntry = {};
        logEntry.prevState = stateTransformer(getState());
        logEntry.action = action;
        // .... 
        returnedValue = next(action);
        // ....
        logEntry.nextState = stateTransformer(getState());
        // ....
        return returnedValue;
      };
    };
  };
}