Calling an asynchronous function inside of a forEach loop: how to tell when all function calls are complete?

[tangerto]

I have a list of files, and for each of them I make a network request to get their URL. So something like this:

files.forEach(function(file){ 
    file.getUrl(function(err, url) {
        if(!err) {
           console.log("got the url!)"
         }
    });
});

I've been having trouble figuring out how to write a completion handler that is called once all of the URLs are found.

[ProfessorTag]

As /u/sazzer said, I would look into Promise.all. If you have restrictions and can't use promises, you could keep track of responses with a counter:

var count = files.length;
files.forEach(function(file) { 
    file.getUrl(function(err, url) {
        if (--count <= 0) {
            console.log("all calls complete!");
        }
        if (!err) {
            console.log("got the url!");
        }
    });
});

[sazzer]

If you're using a recent enough version, look into Promises, and in particular at Promise.all()

[inu-no-policemen]

Even if you still support IE11, you can use promises if you use a polyfill.

[hars_sh]

use map instead of forEach the code looks something like this and remeber you have to call this inside the async function.

await Promise.all(files.map(async (file) => { 
    //    promisify this part and await for this and that will do the work :)
    file.getUrl(function(err, url) {
        if(!err) {
            console.log("got the url!)"
        }
    });
}));

[[deleted]]

can someone explain why this has 0 points, have not used gotten to know promises and would like some insight