Render the results of two separate async.each methods - node.js

Question

I am new to nodejs and async. Having trouble understanding how can I wrap the two separate async.each methods to have one res.render...I am trying to display a list of valid account ids, and valid user ids on the front end.
The two separate async.each methods are:
async.each(account_ids, function(accountId, callback) {
console.log('Processing accountId ' + accountId);
callingExternalApi(accountId, callback, function(err, response){
if(err){
console.log("error account");
}
console.log("account response is: ", response);
});
}, function(err) {
if( err ) {
console.log('An account failed to process');
} else {
console.log('All accounts have been processed successfully');
}
});
and
async.each(email_ids, function(emailId, callback) {
console.log('Processing email id ' + emailId);
request({
url: emailIdlookupUrl,
method: 'POST',
json: {
email_address: emailId
}
}, function (err, response, body) {
if (err) {
logger.error(err);
req.flash('error', err.message);
return res.redirect('?');
}
if (response.statusCode !== 200) {
const msg = 'Unable to verify user';
req.flash('error', msg);
return res.redirect('?');
}
console.log("user id is: ", body.user.id);
callback();
});
}, function(err) {
if( err ) {
console.log('An email failed to process');
} else {
console.log('All user emails have been processed successfully');
}
});
Any help is highly appreciated. Please excuse me for any redundant callbacks or error logging. Still learning nodejs.
Thanks!!

Answer 1

The main issue is not that you are invoking both of these async.each calls. The problem is that they will run in parallel, and the fastest one to invoke req.* functions or callback function will return a response to the connection.
Both of these functions return promises if their callback parameters are omitted.
I recommend reading up on both the async library and JS async/await in general:
https://javascript.info/async-await
https://caolan.github.io/async/v3/docs.html#each
https://zellwk.com/blog/async-await-express/
Note that async also accepts native async functions, which many finder cleaner and easier to understand.
Here is what I think you want from the code above, including compiling the results into lists:
var request = require("request-promise");
async function checkAccounts(account_ids) {
const valid_accounts = [];
await async.each(account_ids, async function(accountId) {
console.log("Processing accountId " + accountId);
const extAPIresult = await callingExternalApi(accountId);
console.log("account response is: ", extAPIresult);
});
valid_accounts.push(extAPIresult);
console.log("All accounts have been processed successfully");
return valid_accounts;
}
async function checkEmails(email_ids) {
const valid_emails = [];
await async.each(email_ids, async function(emailId) {
console.log("Processing email id " + emailId);
const reqresult = await request({
url: emailIdlookupUrl,
method: "POST",
json: {
email_address: emailId
}
});
if (reqresult.statusCode !== 200) {
throw new Error("Unable to verify user");
}
valid_emails.push(reqresult.body.user.id);
console.log("user id is: ", reqresult.body.user.id);
});
console.log("All emails have been processed successfully");
return valid_emails;
}
async function doChecks() {
const accounts = checkAccounts(account_ids);
const emails = checkEmails(email_ids);
const responses = await Promises.all([accounts, emails]);
console.log("All checks have been processed successfully");
return responses;
}
function get(req, res) {
doChecks()
.then(responses => {
res.send("All checks have been processed successfully");
res.send(String(responses));
})
.catch(err => {
req.flash("error", err.message);
res.redirect("?");
});
}