How to wait until a callback is fully finished?

Question

I have the following loops which make 10 requests. The console.log would print from 1 to 10. How do I modify this code to only print out the final length of peopleProfile (10)?

for (var i = 0; i < 10; i++) {
  request(URL, function(err, response, body) {
    if (err) {
      console.log(err);
    }
    if (!err && response.statusCode == 200) {
      peopleProfile.push(body);
      console.log(peopleProfile.length);
    }
  });
}

You can't do async and loop, you are basically doing 10 requests concurrently, not sequentially. — elclanrs, Feb 17 '16 at 01:53
Can you point out a better way to solve this? I'd like to make 10 requests and store each request's response to `peopleProfile`. — Bun, Feb 17 '16 at 01:55
I'd aim for something like `sequence(range(1,10).map(request(url))` where `request(url)` returns a promise, and `sequence` takes an array of promises and runs them in order. — elclanrs, Feb 17 '16 at 01:56
You could count the resolved requests, and the rejected requests and check when the combined total hits 10 — iH8, Feb 17 '16 at 01:57
Here's one solution: [How can I throttle stack of api requests?](http://stackoverflow.com/questions/35422377/how-can-i-throttle-stack-of-api-requests/35422593#35422593). — jfriend00, Feb 17 '16 at 02:01
http://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call — mattwilsn, Feb 17 '16 at 02:15

score 2 · Accepted Answer · answered Feb 17 '16 at 02:11

2

you can use Bluebird - a promise library for this

var promises = [];
for (var i = 0; i < 10; ++i) {
    promises.push(requestAsync(url));
}
Promise.all(promises).then(function() {
    console.log("print this after finishing 10 requests");
});

answered Feb 17 '16 at 02:11

Tuan Anh Tran

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1

this is exactly what I was talking about in my comment! I just do not have the energy to post a solution! – Feb 17 '16 at 02:16

score 1 · Answer 2 · answered Feb 17 '16 at 02:09

Is there a reason you can't do this?

var completedRequests = 0;

for (var i = 0; i < 10; i++) {
  request(URL, function(err, response, body) {
    completedRequests++;
    if (err) {
      console.log(err);
    }
    if (!err && response.statusCode == 200) {
      peopleProfile.push(body);
      if (completedRequests === 10) {
        console.log(peopleProfile.length);
      }
    }
  });
}

How to wait until a callback is fully finished?

2 Answers2