Pinia

export const initData = function () {
    const instance = useCounterStore()

    // listen on change, then save to localStorage
    instance.$subscribe((mutation, state) => {
        localStorage.setItem(instance.$id, JSON.stringify(state)) 
    })


// load from localStorage
    let data = localStorage.getItem(instance.$id);
    if (data) {
        instance.$patch({
            ...JSON.parse(data)
        })
    }
}

Then in main.ts, after app created, call this initData function:

import { initData } from './store/Counter'

...
app.use(createPinia)
app.mount('#app')

initData()