JS decorator: async extend class

js

import forEach from 'lodash/lodash'

class Defer {
  constructor () {
    this.resolve = null
    this.reject = null

    this.promise = new Promise((resolve, reject) => {
      this.resolve = resolve
      this.reject = reject
    })

    Object.freeze(this)
  }
}


function asyncExtend (mixins) {
  return (target) => {
    const defer = new Defer()
    const proto = target.prototype
    const _super = { ...proto }

    target.waitAsyncExtend = defer.promise

    if (!mixins) {
      defer.resolve()
    } else {
      (async function () {
        const loadedMixins = await Promise.all(mixins.map(f => f()))

        forEach(loadedMixins, ({ mixin }) => {
          forEach(mixin, (func, key) => {
            proto[key] = async function () {
              _super[key] && await _super[key].call(this)
              func.call(this)
            }
          })
        })

        defer.resolve()
      })()
    }

    return target
  }
}

@asyncExtend([
  () => import('any/path/to/mixin')
])
class Any {
  async hi () {
    await Any.waitAsyncExtend

    console.log('HI...')
  }
}