How to rewrite a function under async/await?

Question

I want to stop using the async library, replacing it with vanilla js.

const async = require('async')

function getTopicsData(tids, Uid, callback) {
  async.map(tids, (tid, next) => {
    redis.hgetall(`topic:${tid}`, (err, topics) => {
      redis.sismember(`topic:${tid}:subscribers`, Uid, (err, subscriber) => {
        topics.subscriber = !!subscriber

        next(false, topics)
      })
    })
  }, callback)
}

module.exports = getTopicsData

It doesn't look like you can use `async/await` in the code you posted. You can `getTopicsData` return a promise so it can be `await`ed but that's about it. — Felix Kling, Oct 12 '17 at 21:12
Well, it's a bit hard if you intend to use callbacks, what have you tried? — Icepickle, Oct 12 '17 at 21:13
@FelixKling Once`hgetall` and `sismember` are promisified, using async/await seems quite applicable — Bergi, Oct 12 '17 at 21:16

score 2 · Accepted Answer · answered Oct 12 '17 at 21:31

2

The solution I would implement would also include bluebird. Here is how I would use it.

const Promise = require('bluebird')

const hgetall = Promise.promisify('redis.hgetall')
const sismember = Promise.promisify('redis.sismember')

module.exports = async function (tids, Uid) {
  return Promise.map(tids, async function (tid) {
    let {topics, subscriber} = await Promise.props({
      topics: hgetall(`topic:${tid}`),
      subscriber: sismember(`topic:${tid}:subscribers`, Uid)
    })

    topics.subscriber = !!subscriber

    return topics
  })
}

answered Oct 12 '17 at 21:31

InternalFX

1,475
12
14

I'd recommend to use the more idiomatic `Promise.all` over `Promise.props`, it's a bit shorter and also works with native promises – Bergi Oct 12 '17 at 21:35
This amounts to personal taste, I prefer `props` because it takes an object. I prefer to name my results. – InternalFX Oct 12 '17 at 21:40
ironically, this solution doesn't even need to be an async function – InternalFX Oct 12 '17 at 21:46

How to rewrite a function under async/await?

1 Answers1