Why data isn't being added to array in NodeJS - arrays

Question

What is wrong with my code:
var emailExistence = require('email-existence');
var emails = ['klevisi#gmail.com', 'workingemail#gmail.com'];
var validEmails = [];
emails.forEach(function(email) {
emailExistence.check(email, function(err, res) {
if(res == true) {
validEmails.push(email); //No email is being added
console.log(email); //Emails are written to the console
}
});
});
validEmails.forEach(function(email) {
console.log(email); //Nothing is written to the console
});
The validEmails array isn't being populated.

Answer 1

It is because
validEmails.forEach(function(email) {
console.log(email); //printed at last
});
is outside the callback.So it executed before executing the callback.You will have to use validEmails after every thing has been added or all callback completed.
You can use underscore's after for these kind of things.
you can try with
var _U = require('underscore');
var afterAllEmailChecks = _U.after(emails.length,function(){
validEmails.forEach(function(email) {
console.log(email); //Nothing is written to the console
});
});
emails.forEach(function(email) {
emailExistence.check(email, function(err, res) {
if(res == true) {
validEmails.push(email); //No email is being added
console.log(email); //Emails are written to the console
}
afterAllEmailChecks();
});
});