GAS-BasicCalc.gs

function doGet() {
  var app = UiApp.createApplication().setTitle("The Adding Machine");
  var formPanel = app.createFormPanel();
  var verticalPanel = app.createVerticalPanel();
  var label1 = app.createLabel("First Number: ");
  var textBox1 = app.createTextBox().setName('textBoxResult1');
  var label2 = app.createLabel("Second Number: ");
  var textBox2 = app.createTextBox().setName('textBoxResult2');
  var submitButton = app.createSubmitButton("Click to add the numbers together.");
  verticalPanel.add(label1).add(textBox1).add(label2).add(textBox2).add(submitButton);
  formPanel.add(verticalPanel);
  app.add(formPanel);
  return app;
}

function doPost(e) {
  var app = UiApp.getActiveApplication();
  var sum = e.parameter.textBoxResult2 * 1 + e.parameter.textBoxResult1 * 1;
  var label1 = app.createLabel(e.parameter.textBoxResult1 + " + " + e.parameter.textBoxResult2 + " = " + sum);
  app.add(label1);
  return app;
}