Lazy getters

lazy-getter-example.js

import { makeFoo, makeBar } from "./providers.js"

/**
* Create property `name` on `obj` that will run `provider`'s factory method the first time 
*/
function makeLazyGetter(obj, name, provider){
  let value
  Object.defineProperty(obj, name, {
    get: function(){
      if(!value){
        value= factory()
      }
      return value
    }
  })
}

export function injectProvidersMiddleware(req){
  makeLazyGetter(req, "foo", makeFoo)
  makeLazyGetter(req, "bar", makeBar)
}