forkJoin with percentage

forkJoin with percentage.js

let Rx = window.Rx = window['rxjs'];
let {forkJoin, Subject, merge, of} = Rx;
let {ajax} = Rx.ajax;
let {map, filter, tap, takeLast, scan, startWith} = Rx.operators;
console.clear();

function forkJoinTransparent(arrayOfObservables) {


   const emptyArray = Array.from(Array(arrayOfObservables.length));
   const initialValue = {data:emptyArray, percentage: 0};
  
    const modilefiedObservablesList = arrayOfObservables.map(
        (item, index) => item.pipe(
          takeLast(1),
          map(data => ({data: data, index})),
        )
    );


 return merge(...modilefiedObservablesList).pipe(
   startWith(initialValue),
   scan((acc, next) => {
       const newAcc = {data: [...acc.data], percentage: acc.percentage};
       
       newAcc.data[next.index] = next.data;
       const definedValues = newAcc.data.filter(x => !!x)
       newAcc.percentage = definedValues.length * 100/ newAcc.data.length;

       return newAcc;
     }, initialValue)
   )
}

const getUserDetails = userIdsList => {
  
  const arrayOfObservables = userIdsList.map(userId =>
    ajax('https://jsonplaceholder.typicode.com/comments/' + userId)
  )
  
  return forkJoinTransparent(arrayOfObservables)
}


const result$ = getUserDetails([1, 2, 15]);

result$.pipe(
  tap((data) => console.log('percentage: ', data)),
  filter(data => data.percentage === 100)
)
.subscribe((data) => console.log('final value: ', data.data));