Cooking with GAS - Subverting User-permission Authorization in Spreadsheet onEdit function

index.js

// Ideally one would get user information from onEdit using onEdit's event's .user attribute,
// however GAS does not give authorization to do so for the onEdit function (without some minor caveats).
// The following subverts this slightly by allowing the user to include their own user information that is
// then stored on the user's properties for the file/script.

function onEdit(e) {
  var user = PropertiesService.getUserProperties().getProperty('user');
  if (!user) {
    var ui = SpreadsheetApp.getUi();
    while (!user) {
      var response = ui.prompt('Please enter your name:');
      user = response.getResponseText();
    }
    // This next line is cruital to not spamming the user each time they edit a cell
    PropertiesService.getUserProperties().setProperty('user', user);
  }
  // Set a comment on the edited cell to indicate when it was changed.
  var range = e.range;
  range.setNote('Value updated to: ' + e.value + '\nBy user: ' + user + '\n' + 'Modified at: ' + new Date());
}