Estimate Browser Storage capacity

StorageEstimate.js

import { types } from 'mobx-state-tree'
import bytes from 'bytes'

/*
 * See: https://developers.google.com/web/updates/2016/06/persistent-storage
 * See: https://developers.google.com/web/updates/2017/08/estimating-available-storage-space
 */
const StorageEstimate = types
  .model('StorageEstimate', {
    usage: types.maybe(types.number),
    quota: types.maybe(types.number),
  })
  .views(self => ({
    get usageMB() {
      return bytes(self.usage, { unit: 'mb' })
    },
    get quotaMB() {
      return bytes(self.quota, { unit: 'mb' })
    },
  }))
  .actions(self => {
    return {
      afterCreate() {
        const { storage } = navigator

        if ('storage' in navigator && 'estimate' in storage) {
          storage.estimate().then(({ usage, quota }) => self.update(usage, quota))
        } else {
          throw new Error(`Cannot estimate available storage space.`)
        }
      },
      update(usage, quota) {
        self.usage = usage
        self.quota = quota
      },
    }
  })

export default StorageEstimate