var files=[];
var mapRef=[];
var overlay=[];

var listMapsRef = storageRef.child(prefix+"/listfile.txt");
listMapsRef.getDownloadURL().then(function(url) {
    $.get(url, function(txt){
        files = txt.split("n");
        for (var i = 0; i < files.length; i++) {
            mapRef.push(storageRef.child(files[i]));
            .....
            .....
        }
        count = mapRef.length;
        mapRef.forEach(function(oneMap) {
                oneMap.getDownloadURL().then(function(url){
                ovl=loadImage(url);
                overlay.push(ovl);
                if (!--count) {
                    startMyApp();
                    }
                });
            });

    }); //.get
});  //.then