// pages/+onCreateGlobalContext.server.js
// Environment: server
export async onCreateGlobalContext() {
  const dataFromAPI = await fetchDataFromAPI()
  const someGlobalData = select(dataFromAPI)
  globalContext.someGlobalData = someGlobalData
}

// pages/+config.js
export default {
  passToClient: 'someGlobalData'
}

// Anywhere (client,server)
import { getGlobalContext } from 'vike'
const { someGlobalData } = await getGlobalContext()