What problem does this feature solve?

In vue2.x, I can use Vue.prototype, in vue3.x, should I export the app of main.js, and import app in normal js? Or there's other way.

What does the proposed API look like?

none

app.config.globalProperties.$foo = 'hello'

usage

created(){
  console.log(this.$foo)
}

If you want to use it outside the component, maybe you can bind the data to the window or use Vuex to solve it.

Please, next time consider using the forum, the Discord server or StackOverflow for questions first. But feel free to come back and open an issue if it turns out to be a bug 🙂