Middlware Arrow Function And Destructuring

const createMiddleware = (extraArgument) => ({dispatch, getState}) => (next) =>(action) => {//some code};

const createMiddleware = (extraArgument) => {
  return ({dispatch, getState}) => {
    return (next) => {
      return (action) => {//some code};
    }
  }
}

{dispatch, getState} 是解構賦值 (Destructuring)

上層呼叫方 applyMiddleware.js 傳參數 middlewareAPI。

return middleware(middlewareAPI);

middlewareAPI 當中有兩個物件 dispatch, getState，
下層被呼叫用 {dispatch, getState} 可以取得。




ref .1 https://developer.mozilla.org/zh-TW/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment