devices.js

const find = require('local-devices');
const fetch = require('node-fetch');

let heatpumpIPs = [];

const getHeatpumps = () => find().then( async devices => {
    for ( let i = 0; i < devices.length; i++) {
        try {
            let response = await fetch('http://' + devices[i].ip + '/common/basic_info')
            let isHeatpump = await response.ok
            if( ! isHeatpump ) {
                throw new Error(devices[i].ip + ': Not a Heat Pump')
            }
            heatpumpIPs.push(devices[i].ip)
        } catch (e) {
            //
            console.log(e.message);
        }
    }
    return devices
})

async function go() {
    devices = await getHeatpumps()
    console.log(heatpumpIPs)
}

go();