如何获得承诺以请求-承诺-自然解决

Question

I'm using request-promise-native module on node.js. The API I'm calling returns the required data via a GET. That works just fine.

However, when I try to get the data from the function which because it is preceded with Async returns a promise, I just can't get the syntax right. Here's what I've tried:

const request = require('request-promise-native');

async function usdToEos () {
  const options = {
    method: 'GET'
    ,uri: 'https://api.coincap.io/v2/assets/eos'
    ,json: true
  }
  const response = await request(options)
    .then(response => {
      console.log(response)
      return (1 / response.data.priceUsd)
    })
    .catch(error => {
      console.log('\nCaught exception: ' + error);
    })
}

var usdToEosMul = usdToEos()
console.log('\n' + 'USD multiplier to convert to EOS' + '\n')
console.log(usdToEosMul)

How do I get the returned value to be ... the data ... (1 / response.data.priceUsd). This is visible in the ... console.log(response) ... but not in the variable usdToEosMul.

Answer 1

the function which because it is preceded with async returns a promise

Seems like you nearly answered your question already. You will have to wait for that promise at your call site:

usdToEos().then(usdToEosMul => {
  console.log('\n' + 'USD multiplier to convert to EOS' + '\n')
  console.log(usdToEosMul)
}).catch(error => {
  console.log('\nCaught exception: ' + error)
})

function usdToEos() {
  const options = {
    method: 'GET'
    ,uri: 'https://api.coincap.io/v2/assets/eos'
    ,json: true
  }
  return request(options).then(response => {
    console.log(response)
    return (1 / response.data.priceUsd)
  })
}

or

;(async function() {
  try {
    const usdToEosMul = await usdToEos()
    console.log('\n' + 'USD multiplier to convert to EOS' + '\n')
    console.log(usdToEosMul)
  } catch(error) {
    console.log('\nCaught exception: ' + error)
  }
}())

async function usdToEos() {
  const options = {
    method: 'GET'
    ,uri: 'https://api.coincap.io/v2/assets/eos'
    ,json: true
  }
  const response = await request(options)
  console.log(response)
  return (1 / response.data.priceUsd)
}