cache-facade.js

const createCache = () => {
  const cacheMap = new Map()
  return {
    remember(key, setter) {
      if (this.has(key)) {
        return this.get(key)
      }
      const value = setter.call(null)
      this.set(key, value)
      return value
    },
    has(key) {
      return cacheMap.has(key)
    },
    set(key, value) {
      cacheMap.set(key, value)
    },
    get(key) {
      return cacheMap.get(key)
    },
  }
}

const cache = createCache()
let result1 = null

if (cache.has('post')) {
  result1 = cache.get('post')
} else {
  result1 = { id: 1 }
  cache.set('post', result1)
}

const result2 = cache.remember('post', () => ({ id: 1 }))

console.log(result1)
console.log(result2)