redux的createStore

function createStore(reducer,initialState){
    let state = initialState || undefined
    let listener = []
    function getState(){
        return state
    }
    function subscribe(cb){
        listener.push(cb)
        return function(){
            let index = listener.indexOf(cb)
            listener.splice(index,1)
        }
    }
    function dispatch(action){
        state = reducer(state,action)
        listener.forEach((cb)=>{
            cb()
        })
        return action
    }
    dispatch({type:'@redux'})
    return {
        getState,
        subscribe,
        dispatch
    }
}

function reducer(state,action){
    switch(action.type){
        case '1' :
            return 'bai'
        case '2' :
            return 'ming'
        default :
            return state || '^^__^^'
    }
}
let store = createStore(reducer,25)
console.log(store.getState())
function render(){
    console.log(store.getState())
}
let unsubscribe = store.subscribe(render)
console.log(store.dispatch({type:'1'}))
unsubscribe()
console.log(store.dispatch({type:2}))