showModalDialog() method does not suspend the server-side script while the dialog is open.
The script should show all the elements one by one. But a newer dialog might close the older one. So, you probably only see the last one. If you want to show all the elements in one dialog, use JSON.stringify():
SpreadsheetApp.getUi().showModalDialog(
HtmlService.createHtmlOutput(
JSON.stringify(arr,null,2)
), 'Test'
);
Or if you want to see them one by one, use Utilities.sleep():
for (var count = 0; count < 10; count++) {
var htmlOutput = HtmlService.createHtmlOutput(arr[count]);
var arrayOutput = SpreadsheetApp.getUi().showModalDialog(htmlOutput, 'Test');
Utilities.sleep(15*1000);
}
arrarray ?