Javascript: For loop with asynchronous calls

Asked Apr 12 '17 at 13:22

Active Apr 12 '17 at 13:26

Viewed 43 times

I am fairly new in using javascript. I just want to write values in json file but could not do so. Second for loop run out while fs.readFileSync is getting data. Do I need callback for that and How it should be written. Here is my code :

for (i = 0; i < details.waypoints.length; i++) {
    if (details.waypoints[i].ts.getTime() - start_time.ts.getTime() > 115000) {
        for (j = 0; j < i; j++) {
            fs.readFile(Path.join(__dirname) + '/Modified_Data.json', 'utf8', function readFileCallback(err, data) {
                if (err) {
                    console.log(err);
                } else {
                    obj.table.push({
                       PathId: start_index,
                    }); //add some data
                    json = JSON.stringify(obj); //convert it back to json
                    fs.writeFile('Modified_Data.json', json, 'utf8', callback); // write it back
                }
            });

        }

    }

}

edited Apr 12 '17 at 13:26

asked Apr 12 '17 at 13:22

Developer

1

You're using `readFileSync` but then `writeFile`. Look into _promises_ if you want to do those writes async. – Sergiu Paraschiv Apr 12 '17 at 13:25
1

Possible duplicate of [Asynchronous Process inside a javascript for loop](http://stackoverflow.com/questions/11488014/asynchronous-process-inside-a-javascript-for-loop) – Whymarrh Apr 12 '17 at 13:45
Thank you very much I got it now – Developer Apr 12 '17 at 13:50

Javascript: For loop with asynchronous calls

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