Vue3.0简单替代Vuex 共享状态必须符合两个条件：
响应式：当状态改变时，使⽤它们的组件也应更新
可⽤性：可以在任何组件中访问状态
import { reactive, provide, inject, readonly } from 'vue'
export const stateSymbol = Symbol('state')
export const createStore = () => {
const state = reactive({
count: 0
});
const increment = () => unt++;
return {
increment,
state: readonly(state)
}
}
export const useState = () => inject(stateSymbol)
vue中reactiveexport const provideState = () => provide(createStore)