redux中applyMiddleware写法到底是哪种？

Question

在学习redux中间件的时候，发现了applyMiddleware写法竟然有两种，但是官方文档只有这一种
const store = createStore(reducer, preloadedState, applyMiddleware(...middleware))

但是自己在其他地方由看到这种写法
const store = applyMiddleware(...middlewares)(createStore)(reducer, initialState)
想问下各位这是什么写法，是以前的旧写法还是什么写法？

Answer 1

这两种写法是等价的，createStore的源码

export default function createStore(reducer, preloadedState, enhancer) {
  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)
  }
  ...
}

最关键的就是下面这一行

enhancer(createStore)(reducer, preloadedState)