Get spreadsheet key of the embedded spreadsheet

Example code:

function doGet() {

  //get the active page

  var page = SitesApp.getActivePage();

  // Get the content of the current page

  var htmlContent = page.getHtmlContent();

  var filteredContentArray = htmlContent.match(/src=\'http:\/\/spreadsheets.google.com\/spreadsheet\/loadredirect\?chrome=false&key=[0-9A-Za-z]+/g);

  var ssKeys = []

  for(var i in filteredContentArray){

    var key = filteredContentArray[i].match(/key=[A-Za-z0-9]+/)[0].substring(4);

    ssKeys.push(key);

  }

  //Create an application to display the spreadsheet keys which are embedded in this page

  var app = UiApp.createApplication();

  for(var i in ssKeys){

    app.add(app.createLabel(ssKeys[i]));

  }

  return app;

}

Sample Embedded Spreadsheets:

Key of the embedded spreadsheets displayed by Apps Script Gadget: Demo