xml2js: put parser into a function

Question

xml2js: put parser into a function

I got this code on my NodeJS server:

function GetXML() {
    fs.readFile('../slideshow.xml.old', function(err, data) {
        parser.parseString(data, function (err, result) {
            var json = JSON.stringify(result);
            console.log(json);
            return json;
        });
    });
}

The console.log() is working well but this is not:

.get('/', function(req, res) {
    res.end(GetXML());
};

It returns undefined which is quite logic because functions are nested (I think ?). But I don't know how to make GetXML() returning a value.

json
node.js
nested-function

Answer 1

It's returning undefined because you're trying to execute synchronously an asynchronous task. You have to pass a callback to your GetXML() function, like:

function GetXML(cb) {
  fs.readFile('../slideshow.xml.old', function(err, data) {
    parser.parseString(data, function (err, result) {
      var json = JSON.stringify(result);
      cb(json);
    });
  });
}

, and call it properly in your .get function:

.get('/', function(req, res) {
  GetXML(function (json) {
    res.end(json);
  });
};

You should take a look at this article that explains how callbacks work in node.js.

Answer 2

"GetXML" is not returning a value. It can be change to:

function GetXML() {
    return fs.readFile('../slideshow.xml.old', function(err, data) {
        parser.parseString(data, function (err, result) {
            var json = JSON.stringify(result);
            console.log(json);
            return json;
        });
    });
}