redux的主要API集中在createStore函数返回值中，以下这个迷你的redux只简单实现createStore、dispatch、subscribe、getState方法，如下：
代码语言：javascript复制const createStore = function(reducer, initialState){
let currentState = undefined;
if(initialState) {
currentState = initialState;
}
let currentReducer = reducer;
let listeners = [];
return {
getState() {
return currentState;
},
dispatch(action) {
if(!currentState){
currentState = currentReducer(currentState, action);
}
currentState = currentReducer(currentState, action);
listeners.forEach((item) => {
item();
});
return this;
},
subscribe(fn) {
listeners.push(fn);
}
}
};测试代码：
代码语言：javascript复制let reducer = function(state, action) {
if(!state) {
return {counter: 0};
}
switch(action.type) {
case 'ADD':
return {counter: state.counter 1};
case 'DEL':
return {counter: state.counter-1};
default:
return state;
}
};
let store = createStore(reducer);
store.subscribe(function(){
console.log('before1')
});
store.subscribe(function() {
console.log('before2')
});
store.dispatch({
type:'ADD'
});
console.log(store.getState());
store.dispatch({
type: 'ADD'
});
console.log(store.getState());
store.dispatch({
type: 'DEL'
});
console.log(store.getState());运行结果：
