Get both return values of a promise chain

Question

I have a promise chain inside of a function and I would like to console.log the values returned from 2 functions inside of the chain. How would I do this? With my current code I get the value from si.cpuTemperature() then undefined but I would like to get the value from si.cpu() then si.cpuTemperature().

const si = require('systeminformation');

function getCPUInfo() {
    return new Promise((resolve) => {
        resolve();
        console.log("Gathering CPU information...");
        return si.cpu()
        // .then(data => cpuInfo = data) - no need for this, the promise will resolve with "data"
        .catch(err => console.log(err)); // note, doing this will mean on error, this function will return a RESOLVED (not rejected) value of `undefined`
    })
    .then(() => {
        return si.cpuTemperature().catch(err => console.log(err));
    });
}

getCPUInfo().then((data1, data2) => console.log(data1, data2));

So, what do you want `data1` and `data2` to be? si.cpu and si.cpuTemperature? — Jaromanda X, Apr 24 '19 at 02:16
Seems like you should just be using `Promise.all([si.cpu(), si.cpuTemperature()]).then(console.log)` — Mark, Apr 24 '19 at 02:17
I'm not understanding the construction of the Promise (or the call of `resolve` immediately), can't you just call `.then` on your existing promises? — CertainPerformance, Apr 24 '19 at 02:18
note: `Get both return values of a promise chain` makes no sense, since there is only one result in a promise chain — Jaromanda X, Apr 24 '19 at 02:27

Swaraj Giri · Accepted Answer · 2020-01-30T08:36:26.730

From the docs,

systeminformation.method() returns a promise. So you don't really need to wrap it inside a promise constructor, ie new Promise()

To get the cpu and temperature, since they are not dependent on each other, you can do either use parallel promises along with an async function or just parallel promises

async function getCpuAndTemperature() {
  const [cpu, temperature] = await Promise.all([
      si.cpu(),
      si.cpuTemperature()
  ])

  console.log(cpu, temperature)
}

or

function getCpuAndTemperature() {
  return Promise.all([
      si.cpu(),
      si.cpuTemperature()
  ])
  .then(([cpu, temperature]) => {
    console.log(cpu, temperature)
  })
}

Get both return values of a promise chain

1 Answers1