NodeJs Use async with for loop download

Question

I have this loop for download some files and it's work fine.

But the files are downloaded like "2,3,4,1,5" order and not "1,2,3,4,5".

I know how to do .each async and waterfall async but I don't know how to do for this loop.

Config.TotalFiles = 5;

for(i = 1; i <= Config.TotalFiles; i++) {
   $this.CreateJSONFile(i, function() {
     cls();
   });
}

And when downloads are done I want to call my callback, I have tried this if(id == Config.TotalFiles) but it's doesn't work because the id isn't good.

How can I done an "async" process with this loop?

Thanks

That depends on how fast each CreatJSONFile call does its job. They're started in the expected order always. If you want to ensure they also end in the expected order, your only choice is to do it sequentially instead of in parallel (using the …Series methods). — Bergi
– Bergi, Commented Jul 25, 2017 at 11:13

Kamesh · Accepted Answer · 2017-07-25 11:21:09Z

1

You can use async.whilst for this:

Config.TotalFiles = 5;
var count = 1;

//pass your maincallback that you want to call after downloading of all files is complete.

var callMe = function(mainCallback){
    async.whilst(
        function() { return count <= Config.TotalFiles; },
        function(callback){
            $this.CreateJSONFile(count, function() {
                cls();
                count++;
                callback();
            });
        }, function(){
           //This function is the final callback
           mainCallback();
        })
}

edited Jul 25, 2017 at 11:21

answered Jul 25, 2017 at 10:11

Kamesh

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3 Comments

EyWN Over a year ago

Sorry but I want just a number (81) ^^

Kamesh Over a year ago

You can check my edited answer. It will do the work.

EyWN Over a year ago

I'm going to answer some questions in a few hour, I need 15 reputation for upvote ^^ :)

Artem · Accepted Answer · 2017-07-25 10:20:43Z

0

Yes, you need to implement async for-loop. The main idea is to call callback (like continue), when current step has been completed. You may use some helpful library as mentioned above (async.js). But you also have to understand that it will not be done in parallel (so the time to complete the downloads will be increased).

These are some nice examples to help you: https://github.com/caolan/async/blob/v1.5.2/README.md#whilst

answered Jul 25, 2017 at 10:20

Artem

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1 Comment

EyWN Over a year ago

Can you check my answer please? I have added more code

EyWN · Accepted Answer · 2017-07-25 11:12:57Z

Check my screen please for understand my case.

https://i.sstatic.net/azHUA.jpg

Or this pastebin https://pastebin.com/jtANeSxq

                cls();
                for(i = 1; i <= Config.TotalFolders; i++) {
                    $this.CreateJSONFile(i, function() {
                        setTimeout(function() {
                            cls();
                        }, 200);
                    });
                }

    CreateJSONFile(id, callback) {
    console.log(chalk.hex("#607D8B")(`Creating JSON Files... [${id}/${Config.TotalFolders}]`));
    var requestOptions = {
        encoding: "binary",
        method: "GET",
        uri: `${Config.Url.Source}${Config.Url.Audio}` + `${id}/skeud.json`
    };
    request(requestOptions, function (error, response, body) {
        if (!error && response.statusCode === 200) {
            if(!fs.existsSync(Config.DownloadsPath + `${id}/skeud.json`)) {
                fs.writeFile(Config.DownloadsPath + `${id}/skeud.json`, body, function(err) {
                    if(err) {
                        return console.log(err);
                    }
                    console.log(chalk.hex("#FFEB3B")(`JSON File ${chalk.inverse(id)} ${chalk.hex("#FFEB3B")("created")}`));
                });
            } else {
                console.log(chalk.hex("#FFEB3B")(`JSON File ${chalk.inverse(id)} ${chalk.hex("#FFEB3B")("skipped")}`));
            }
        }
    });
    /*if(created == Config.TotalFolders) {
        callback();
    }*/
}

Thanks

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