中间件定义

本节目标：理解“中间件定义”的核心思路，并能把它用于实际开发或面试表达。 新建一个中间件

Src/redux-thunk.js
function

thunk({

getState,

dispatch })

{
//

调用下一个中间件，next等于store的原始dispatch方法 return function

(next)

{
   //

这个就是改造后的dispatchreturn function

(action)

{if

(typeof

action ===

'function')

{return

action(dispatch,

getState);

   `}`
  `return`

next(action);

 `}`

}
}
export

default

thunk;

Src/redux-logger.js
function

logger({

getState,

dispatch })

{//dispatch

指提改造后的dispatchreturn function

(next)

{return function

(action)

{

console.log('prev

state',

getState());

next(action);

console.log('next

state',

getState());

 `}`

}
}
export

default

logger;

Src/redux-promise.js
/**

* dispatch 重新派发 * next 下一步 * @param {*} param0* @returns

*/
function

promise({

getState,

dispatch }) {return function

(next)

{return function

(action)

{if

(action.then

&& typeof

action.then

===

'function')

{

action.then(dispatch).catch(dispatch);

   `}` `else` `if`

(action.payload

&& typeof

action.payload.then

===

'function')

{

action.payload

.then(payload

=\>

dispatch({

...action,

payload }))

.catch(error

=\> {

dispatch({

...action,

error:

true,

payload: error });return

Promise.reject(error);

       `})`
  `}` `else` `{`

next(action);

   `}`
`}`

}
}
export

default

promise;