[Fixed] Parallel rxJs Observables without waiting for all to complete

Issue

Is there a way to request many similar requests in parallel using rxJs Observables in parallel without waiting for all requests to complete. I want to handle as each one comes. I don’t want to use a loop of requests. Use case is one of the request is slow and there are many of them
I tried forkJoin (below) but it waits for all to complete. and mergeMap is not taking an array. Any help? Thanks

/*
  // example of many posts
  const post1 = getPostHTTP(1);
  const post2 = getPostHTTP(2); // A slow post
  const post3 = getPostHTTP(3);
  ...
*/

const promises = [];

for (let i = 0; i < 100; i++) {
    promises.push(getPostHTTP(i))
}

forkJoin(promises).pipe(
    finalize(() => {
        //displayPost
    })).subscribe(posts => {
        posts.forEach((post: any) => {
            displayPost(post)
        })
    })

Solution

I think that a mix of from and mergeMap is what you are looking for. The code could look like this

for (let i = 0; i < 100; i++) {
    promises.push(getPostHTTP(i))
}

from(promises).pipe(
  mergeMap(post => displayPost(post)),
).subscribe(
  next: result => {// do something with the result of each displayPost operation},
  error: err => {// handle errors},
  complete: () => {// do something when everything is completed}
)