Function app.provide()

Provide a value that can be injected in all
descendant components within the application.

interface App {
  provide<T>(key: InjectionKey<T> | symbol | string, value: T): this
}

import { createApp } from 'vue'

const app = createApp(/* ... */)
app.provide('message', 'hello')


// Inside a component in the application
import { inject } from 'vue'

export default {
  setup() {
    console.log(inject('message')) // 'hello'
  }
}