How to generate script from existing google form?

As Rubén says , there is no generic way to perform reverse engineering from form to script, but you can write an ad hoc Script using the methods getActiveForm()and getItems(), then I put an ad hoc script inspired by the following answers:

1. Google api - how do you get the text in Forms?
2. How to Edit existing google form item through google script

Scripts:

function generarScript(){
  // Obtener el formulario activo
  var form = FormApp.getActiveForm();
  // Obtener todos los items
  var todosLosItems = form.getItems();

  // Cabecera formulario
  Logger.log('var form = FormApp.create(\'Nuevo fomulario\');');
  Logger.log('var item = ');


  //Obtener las propiedades de cada ítem
  for (var i=0; i<todosLosItems.length;i++){
    var unItem = todosLosItems[i];    

    // La siguiente rutina se debe desarrollar y personalizar para cada tipo de item, : CHECKBOX, MULTIPLE_CHOICE, PAGE_BREAK, DATE, GRID, etc
    // ################# CHECKBOX ###################### //
    if (unItem.getType()===FormApp.ItemType.CHECKBOX) {
      Logger.log('form.addCheckboxItem();');
      Logger.log('item.setTitle(\''+unItem.getTitle()+'\')');
      Logger.log('item.setChoices([');
      var itemTipoCheckBoxOpciones = unItem.asCheckboxItem().getChoices();
      for (var j=0;j<itemTipoCheckBoxOpciones.length;j+=1){
        Logger.log('        item.createChoice(\''+itemTipoCheckBoxOpciones[j].getValue()+'\')');
        if((j+1)<itemTipoCheckBoxOpciones.length){
          Logger.log(',');
        };
      };
      Logger.log('    ]);');
    };

    // ################# MULTIPLE_CHOICE ###################### //
    if (unItem.getType()===FormApp.ItemType.MULTIPLE_CHOICE) {
      Logger.log('form.addMultipleChoiceItem()');
      Logger.log('    .setTitle(\''+unItem.getTitle()+'\')');
      Logger.log('    .setChoiceValues([');
      var itemTipoMultipleChoiceOptions = unItem.asMultipleChoiceItem().getChoices();
      for (var j=0;j<itemTipoMultipleChoiceOptions.length;j+=1){
        Logger.log('\''+itemTipoMultipleChoiceOptions[j].getValue()+'\'');
        if((j+1)<itemTipoMultipleChoiceOptions.length){
          Logger.log(',');
        };
      };
      Logger.log('])');      
    };

    // ################# XXXX ###################### //

  }

  //Pie del formulario
  Logger.log('Logger.log(\'Published URL: \' + form.getPublishedUrl());');
  Logger.log('Logger.log(\'Editor URL: \' + form.getEditUrl());');
};

To see result: Ctrl+ Intro.

Copy text and perform cleanup to finally get:

var form = FormApp.create('Nuevo fomulario');
var item = 
form.addCheckboxItem();
item.setTitle('What condiments would you like on your hot dog?')
item.setChoices([
        item.createChoice('Salsa de tomate')
,
        item.createChoice('Mustard')
,
        item.createChoice('Relish')
    ]);
form.addMultipleChoiceItem()
    .setTitle('Do you prefer cats or dogs?')
    .setChoiceValues([
'Cats'
,
'Dogs'
])
Logger.log('Published URL: ' + form.getPublishedUrl());
Logger.log('Editor URL: ' + form.getEditUrl());

What is the Utility?

One way to use it would be to recycle questions from an existing form.

See also

Auto-generating Google Forms

I understand that it is not possible to create a Google Apps Script code sequence automatically, which would be a form of reverse engineering , but it is possible to make a partial report of the elements of a form.

I say partial because as of today only the Google Apps Script Forms Service is available as an official API and it does not include all the elements that are available through the forms editor. For example, tests cannot be created/read completely.

As for the methods you could use are:

• getActiveForm() to get the form object corresponding to the active form
• getItems() to get all items of type item
• and with the "get" methods of item, their respective properties.

• Response to Populate a Google Form responses from a Google Spreadsheet

See also

Auto-generating Google Forms