Example of all settled promises

all_settled.js

// This will always return a promise that completes when all promises have completed
// because we're turning errors into successful promises (because .catch does not throw an error)
var allSettled = (promises) => {
   return Promise.all(promises.map(p => {
      return p.then(result => {
         return { result: result, error: null }
      })
      .catch(error => {
         return { result: null, error: error }
      })
   }))
}

// if you still want to wait for all results to complete AND have a failed promise this might be how you do it
var allSettledWithFailure = (promises) => {
   var all_promises = Promise.all(promises.map(p => {
      return p.then(result => {
         return { result: result, error: null }
      })
      .catch(error => {
         return { result: null, error: error }
      })
   }))
   .then(results => {
      if (results.find(r => r.error !== null)) {
         return Promise.reject(results)
      } else {
         return Promise.resolve(results)
         // return results <-- this is the same as above except that typescript would complain if the return types didn't match (Promise).
      }
   })
}

// Usage:
// This will show kicking off a couple requests that finish at different times.
// Note "All done" will have a timestamp greater than or equal to all responses to show it waits for everything to complete.
var start = Date.now()

var timeSinceStart = () => {
   return Date.now() - start
}

var RequestPromise = { 
   get: () => { 
      return new Promise((resolve, reject) => {
         setTimeout(() => {
            if (Math.random() > 0.5) {
               reject(new Error('ERROR! ' + timeSinceStart())) 
            } else {
               resolve('Data: ' + timeSinceStart()) 
            }
         }, Math.random() * 3000)
      }) 
   }
} // for copy paste usage

var request_1 = RequestPromise.get('https://google.com')
var request_2 = RequestPromise.get('https://google.com')
var request_3 = RequestPromise.get('https://google.com')
var request_4 = RequestPromise.get('https://google.com')

allSettled([
   request_1,
   request_2,
   request_3,
   request_4,
])
.then(results => {
   console.log('All done: ' + timeSinceStart() + ' ' + JSON.stringify(results))
})