Multi tool use

Promise.all does not check for/store all promises

I have problem with promise.All not catching all the promises to resolve...

short example:

const express = require('express');
const app = express();
const router = express.Router();
const request = require('request');

router.get('/', function(req, res)
{
var promiseArray = ;

function promiseResolve (data) {
return new Promise (function (resolve) {
resolve(data);
});
}

var data1 = 1;

promiseArray.push(promiseResolve(data1));

var data2 = 2;

promiseArray.push(promiseResolve(data2));

var data3 = 3;

promiseArray.push(promiseResolve(data3));

console.log(promiseArray);

**// all is fine**

**// but when we add promise in some asynchronous operation like... request for example:**

var test = request('https://www.google.com', function (err, res, content) {
if (res.statusCode == 200)
{
promiseArray.push(promiseResolve(content));
console.log(content);
}
});

Promise.all(promiseArray).then(function(data) {
console.log(data);
});

**// it does not store promise in a array... I thought that at first promise.All always 'check' if all promises are stored, then execute those by resolve, reject...**

res.render('index');
});
module.exports = router;


comment are in code, but long story short - promise.All does not check for/store all promises.

Some more text for SO 'algorithm'... and more... and more... and more...

Promise.all(promiseArray)

promiseResolve

promiseResolve

Promise.resolve

Promise.all

Promise.all

1 Answer
1

At the time Promise.all(promiseArray) runs, promiseArray is only composed of the first three Promises - the fourth one from request does not get added to promiseArray until after the request goes through, by which time the Promise.all has already resolved. You'll have to explicitly construct a Promise for the request so that promiseArray has all necessary Promises before Promise.all is called:

Promise.all(promiseArray)

promiseArray

request

promiseArray

Promise.all

Promise

request

promiseArray

Promises

Promise.all

promiseArray.push(new Promise((resolve, reject) => {
request('https://www.google.com', function (err, res, content) {
if (res.statusCode == 200) resolve(content);
else reject('bad statusCode');
});
}));


By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.