node.js writeFileSync - node.js

Question

I'm trying to populate a database with pictures paths & names using Node.js.
What I am trying to do is the following :
- A function send a list of pictures as Base64 string.
- Another function receive this list, loop through it, convert it into picture and get the path back.
I'm pretty new to node.js so I might be doing something really stupid.
Here is the reception code :
app.post('/chatBot/moreinfo/create', function (req, res) {
returnList = '';
res.set('Content-Type', 'application/json');
//IF LIST IS NOT EMPTY
if (req.body.imgList.length !== 0) {
const imagePath = '/var/lib/SMImageBank/';
const regex = /^data:image\/(.*);.*$/i;
const listePicture = req.body.imgList;
// LOOPING INTO THE LIST
req.body.imgList.map ( function (element) {
const file = element;
const filetype = file.match(regex)[1];
var picLink2 = '';
const base64data = file.replace(/^data:image\/.*;base64,/, "");
const latin1data = new Buffer(base64data, 'base64').toString('latin1');
const filename = new Date().getTime() + '' + new Date().getMilliseconds() + "." + filetype;
fs.mkdir(imagePath, () => {
fs.writeFile(imagePath + filename, latin1data, "latin1", function (err, content) {
if (err) {
routerLog(req, {'type': 'error', 'content': err} );
res.sendStatus(500);
}
else {
if (process.env.NODE_ENV === "production")
picLink2 = 'http://****.fr/image/' + filename;
else if(process.env.NODE_ENV === "test")
picLink2 = 'http://dev.****.fr:8010/image/' + filename;
else if(process.env.NODE_ENV === "master")
picLink2 = 'http://dev.****.fr:8008/image/' + filename;
else{
picLink2 = 'http://*****.com:8008/image/' + filename;
}
}
});
})
console.log(picLink2);
returnList = returnList + ";" + picLink2;
});
}
MoreInfo.create(req.body, function (ret) {
res.send(ret);
routerLog(req);
})
});
What I want to do is to be able to access the variable "picLink2" from outside the writeFile & mkdir function so I can populate my returnList at each iteration. Obviously as node.js is asynchronous I can't access to picLink2 content from outside fs.writeFile() function. I know there has been a ton of question about this and lot of the answers are to put the code inside the writeFile()/readFile() function but I don't see how I can do it here since the writeFile() function is inside a map that is iterating into a list.
I'm new to the asynchronous world and I don't see how I can solve this problem.

Answer 1

Use writeFileSync for a synchronous operation if that doesn't hurt performance.