Memoized getter decorator

1 - memoized.decorator.js

import { has } from 'lodash-es'

// @flow
export function memoized(
  target: any,
  propertyKey: string,
  descriptor: PropertyDescriptor<*>
) {
  const originalGet = descriptor.get
  const memKey = '__memoized__'

  // eslint-disable-next-line no-param-reassign
  descriptor.get = () => {
    if (!has(this, memKey)) {
      Object.defineProperty(this, memKey, { value: new Map() })
    }

    return this[memKey].has(propertyKey)
      ? this[memKey].get(propertyKey)
      : (() => {
          const value = originalGet.call(this)
          this[memKey].set(propertyKey, value)
          return value
        })()
  }
}

flowconfig

[options]
unsafe.enable_getters_and_setters=true

usage.js

import memoized from 'util/memoized.decorator'

class Example {
  @memoized
  get someProperty() {
    // do something
    return value
  }
}

Based on http://www.couchcoder.com/using-memoized-decorator-cache-computed-properties/