TypeScript decorator to add Vue computed getters to a TypeScript class

decorators.ts

import Vue from 'vue'

export function cached (target: Function) {
  // get descriptors
  const descriptors: any = Object.getOwnPropertyDescriptors(target.prototype)
  const getters = Object
    .keys(descriptors)
    .filter(key => descriptors[key].get && !descriptors[key].set)

  // we have getters!
  if (getters.length) {
    // scope for accessors
    let scope = null

    // build caching layer
    const cache = new Vue({
      computed: getters.reduce((output, key) => {
        // cache reference to original accessors
        const { get } = descriptors[key]

        // create getter
        output[key] = () => get.call(scope)
        return output
      }, {})
    })

    // update descriptors
    getters.forEach(key => {
      const descriptor = descriptors[key]
      descriptor.get = function () {
        scope = this
        return cache[key]
      }

      // update original descriptor
      Object.defineProperty(target.prototype, key, descriptor)
    })
  }
}