Google Script to populate a list in Google Forms from Google Sheets

setListInFormsFromSheets.js

/**
   After any change in the sheet, update the combobox options in the Form
*/
function onChange(e) {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheets()[0];
  var range = sheet.getDataRange();
  var values = range.getValues();
  var comboValues = [];  // <-- cheddar will go here

  // in this example we are interested in column 0 and discarding row 1 (the titles)
  for (var i = 1; i <= values.length; i++) {
    var v = values[i] && values[i][0];
    v && comboValues.push(v)
  }

  // Sort the values alphabetically, case-insensitive
  comboValues.sort(
    function(a, b) {
      if (a.toLowerCase() < b.toLowerCase()) return -1;
      if (a.toLowerCase() > b.toLowerCase()) return 1;
      return 0;
    }
  );
  Logger.log(comboValues);

  // Use your form ID here. You can get it from the URL
  var form = FormApp.openById('<my-form-id>');

  /* 
    Uncomment this to display the item IDs
    and pick the one that you want to modify

  var items = form.getItems();
  for (i = 0; i < items.length; i++) {
    Logger.log("ID: " + items[i].getId(), ': ' + items[i].getType());
  }
  */
  form.getItemById(807137578).asListItem().setChoiceValues(comboValues);

};