What is the most concise way to bind an ES7 async callback to its parent scope context

Question

I want to write code like this using ES7 async callbacks.

class Foo {

  bar(app) {

    // const that = this
    app.on('something', async function() {
      await this.baz() // `this` is `app`. I want it to be the instance of Foo (`that`)
    }

  }

  async baz() {
    console.log('baz')
  }

}

In ES6 we can use anon funcs, but I can't use await inside. I could use promises, but I want the simplicity of await.

app.on('something', () => {
  this.baz()
})

We could use a separate method for the callback. But this is verbose.

class Foo {

  bar(app) {
    app.on('something', this.onSomething)
  }

  async onSomething() {
    await this.baz() // `this` is `app`. I want it to be the instance of Foo (`that`)
  }

  async baz() {
    console.log('baz')
  }

}

So what is the best way given my constraints?

I thought I read somewhere that async/await were not going to be in the ES2016 spec — Jaromanda X, Jul 26 '15 at 14:30
Doesn't an async function need to return something in order for it to resolve? Or throw an error for it to reject ? — Brett Reinhard, Aug 05 '17 at 06:23

score 1 · Answer 1 · answered Jul 26 '15 at 14:26

1

Missed the obvious - I thought I had read something earlier that it was not possible to use anon funcs with async.

app.on('live-app:start', async () => { this })

answered Jul 26 '15 at 14:26

vaughan

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What is the most concise way to bind an ES7 async callback to its parent scope context

1 Answers1