Node.js variable scope [duplicate]

This question already has an answer here:

• JavaScript closure inside loops – simple practical example 21 answers

So currently my code

var app = {};
    app.files = {};

app.loadStaticCss = function(callback) {

    fs.readdir('static/css', function(err, data) {

        for(var i = 0; i < data.length; i++) {

            var name = data[i].replace('.css', '');
                file = data[i];

            fs.readFile('static/css/' + file, 'utf8', function(err, content) {

                app.files['css/' + name] = content;
                callback(file);
            });
        }
    });
}

app.loadStaticJs = function(callback) {

    fs.readdir('static/js', function(err, data) {
        console.log('js')
        for(var i = 0; i < data.length; i++) {

            var name = data[i].replace('.js', '');
                file = data[i];

            fs.readFile('static/js/' + file, 'utf8', function(err, content) {

                app.files['js/' + name] = content;
                callback(file);
            });
        }
    });
}


app.loadStaticCss(function(file) {
    console.log('static (' + file + ') loaded')
});

app.loadStaticJs(function(file) {
    console.log('static (' + file + ') loaded')
});

Should be outputting something like static (style) loaded and static (game) loaded.

But its currently showing or 2x static (game) loaded or 2x static (style) loaded like the variables are messing up