Destructuring async properties in JavaScript/TypeScript

Question

Is there a way to get async properties with destructuring in JavaScript/TypeScript?

Like this:

class A {
  public get x() {
    return this.getX()
  }

  private async getX() {
    return 5
  }
}

async function f(a : A) {
  const { x } = a

  console.log(x) // Promise
}
async function g(a : A) {
  // works as const x = await a.x
  const { await x } = a

  console.log(x) // 5
}

@DimaParzhitsky, I think it will return a Promise since it is waiting for a, not for a.x. — hopeless-programmer
– hopeless-programmer, Commented Nov 6, 2021 at 12:15
Okay, got it. Don't judge me, people often confuse await a.x and (await a).x — Parzh
– Parzh, Commented Nov 6, 2021 at 15:07
I'm afraid, there's no such syntax in JavaScript yet, you have to do const x = await a.x — Parzh
– Parzh, Commented Nov 6, 2021 at 15:08
No, there is not. Also it's weird to have getters that return promises (that are usually involved in side effects), what is your actual use case? — Bergi
– Bergi, Commented Nov 6, 2021 at 22:11

hashed tomato · Accepted Answer · 2021-11-06 22:07:37Z

1

If using utility function is allowed, the following would work.
Its side effect is that the getters for all properties are executed.

const classToObject = async theClass => {
  const originalClass = theClass || {}
  const keys = Object.getOwnPropertyNames(Object.getPrototypeOf(originalClass))
  let classAsObj = {}
  for(const key of keys) {
    classAsObj[key] = await originalClass[key]    
  }
  return classAsObj
}


async function g(a : A) {
  // works as const x = await a.x
  const {x} = await classToObject(a);
  console.log(x) // 5
}

answered Nov 6, 2021 at 22:07

hashed tomato

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