Turn an async function into something you can subscribe to (untested)

createSubscribe.js

const requests = {}

export const createSubscribe = (asyncFn) => {
  return subscribeToData = (params, onUpdate) => {
    onUpdate('pending')

    const key = JSON.stringify(params)
    const request = requests[key]
    if (!request) {
      request = requests[key] = {
        promise: asyncFn(params),
        count: 1,
      }
    }
    else {
      request.count++
    }

    request.promise.then(
      data => onUpdate('received', data)
      error => onUpdate('error')
    )
    
    return () => {
      onUpdate = () => {}
      if (--request.count === 0) {
        delete requests[key]
      }
    }
  }
}