code: function getScript(cfg) {
  
    var script = function(cfg) {
      $('#J_Qrcode').qrcode({
        'render': 'canvas',
        'size': cfg.size || 150,
        'color': '#3a3',
        'text': cfg.text
      });
  
      var canvas = $('#J_Qrcode canvas')[0];
      // here is the most important part because if you dont replace you will get a DOM 18 exception.
      var imageData = canvas.toDataURL('image/png').replace('image/png', 'image/octet-stream');
  
      endCallback(imageData);
    };
  
    return '(' + script.toString() + ')(' + JSON.stringify(cfg) + ');';
  }
docs: get the script to generate canvas in the browser