fs.writeFile doesn't work in loop node.js

Question

I am trying to write multiple files in node.js and saving their path in database. I have some strange situation with writng file-

 var sessionId = req.session.Id;
        var imagelength = req.files.images[0];
        var lengthofarray = JSON.stringify(imagelength.length);
        var arr = [];
        for (var i = 0; i < lengthofarray; i++) {
            var filenameas = "." + imagelength[i].filename.split('.').pop();
            var newGuid = guid();
            var UserFolder = "public/ImagesOfUser" + "/" + "User_" + sessionId;
            var checkourstory = "public/ImagesOfUser" + "/" + "User_" + sessionId + "/" + "OurStory";
            var userImages = "ImagesOfUser" + "/" + "User_" + sessionId + "/" + "OurStory" + "/" + newGuid + filenameas;

            if (!fs.existsSync(UserFolder)) {
                fs.mkdir(UserFolder);
            }
            if (!fs.existsSync(checkourstory)) {
                fs.mkdir(checkourstory);
            }

            fs.readFile(imagelength[i].path, function (err, data) {
                fs.writeFile(checkourstory + "/" + newGuid + filenameas, data, function (err) {
                });
            });
            connection.init();
            connection.query('insert into usergallary (UserId,Image_Path,SectionName) values(?,?,?)', [sessionId, userImages, "OurStory"], function (reqest, reslt) {
            });
        }

Note I am saving file's path in database that is coming through loop and it saves multiple entries for files. But when I try to write files in loop within same loop where database is being executed as it is here above then it doesn't write multiple times.

It only writes one file from loop. How do I write multiple files coming in array?

You're mixing synchronous and asynchronous I/O. I recommend you learn about how concurrency works in NodeJS. This sort of loop isn't possible in a very straightforward way (unless you use something like promises) (also, do you want it in parallel or one after the other?) — Benjamin Gruenbaum, Jul 29 '14 at 08:34
Would a solution using promises be acceptable to you? Also, do you want to run the read/write ops concurrently or one by one? — Benjamin Gruenbaum, Jul 29 '14 at 08:35
@BenjaminGruenbaum, I am new to node.js, The only thing that I want to know is why it is acting this way and an alternate solution would be helpful for now. — user3163213, Jul 29 '14 at 08:38
@user3163213 have you read http://stackoverflow.com/questions/14220321/how-to-return-the-response-from-an-ajax-call ? — Benjamin Gruenbaum, Jul 29 '14 at 09:00

fs.writeFile doesn't work in loop node.js

0 Answers0