Trouble getting curl applescript to execute in JSX

Hi all, 

I am trying to curl images down from a website for a photoshop JSX application. If I type the following applescript into a .applescript file, then it works fine. However, I am throwing my 10 seconds elapsed error if I try to run the getMacImage function below. If I inspect the dl.app script that was created, it works fine. I've also tried saving as dl.applescript and it throws an error. The AS is here: 

do shell script "curl -L -o '/Users/MyUserName/Desktop/test.jpg' 'https://www.google.co.in/intl/en_com/images/srpr/logo1w.png'"

 Here is my jsx code: 

var getMacImage = function(exporturl, assetFolderPath, fileName) {
    try {
        var ff = File(assetFolderPath + '/' + fileName);
        if (!ff.exists) {
            var curlCommand = "\"curl -L -o '" + ff.fsName + "' " + "'" + exporturl + "'";
            var asCode = 'do shell script ' + curlCommand + '"';
            var vbsf = new File(Folder.desktop + "/dl.applescript");
            vbsf.open('w');
            vbsf.write(asCode);
            vbsf.close();
            //alert(asCode);
            vbsf.execute();
        }
        var c = 0;
        while(!ff.exists) {
            $.sleep(1);
            c++;
            if (c > 1000) {
                throw new Error("More than 10 seconds to download image");
            }
        }
        return ff;
    }
    catch(e) {
        throw new Error("Error downloading asset from " + exporturl + ". " + e);
    }
};


var unitTest = function() {
    var afp = Folder.desktop.fsName;
    var imgp = "https://www.google.co.in/intl/en_com/images/srpr/logo1w.png";
    try {
        var f = getMacImage(imgp, afp, "test1.jpg");
    } catch(e) {
        alert(e);
    }
    alert(f.exists);
}
unitTest();