Question

I’m iterating over a list of URLs in an array and for each URL I’m downloading the entire page.

var urlInformations = [];
var count = 0;
urls.forEach(function(url) {
    // download and add to urlInformations
    count++
    if (count == urls.length) {
        // do something after all URLs are processed
    }
});

Right now the way I’m handling this is by maintaining a count of elements, increment it in the anonymous function and at the end of that function if the count reaches the number of URLs I have I would do what I need. There could be race condition and concurrency issues here, right? How should this be done?

Answer 1

No. Javascript is single-threaded, which means if you increment a counter and then compare it against some number to determine whether or not to continue, you’ve basically just implemented a semaphore. There won’t be concurrency issues doing this.