UTIL = {
    urlEncode: function(o) {
        var a = [];
        for (var k in o) {
            if (!o.hasOwnProperty(k)) { continue; }
            a.push(k + '=' + encodeURIComponent(o[k]));
        }
        return a.join('&');
    }
};

QR = {
    getUrl: function(d, w, h) {
        var u = "https://chart.googleapis.com/chart";
        var p = {
            cht: 'qr',
            chs: (w || 150) + 'x' + (h || 150),
            chl: d
        };
        u += '?' + UTIL.urlEncode(p);
        return u;
    },
    
    update: function() {
        var u = QR.getUrl($('#qr-data').val(), $('#qr-width').val(), $('#qr-height').val());
        $('#qr-container').html('<img src="' + u + '" />');
    }
};