AUTO-Generate Unique IDs in Google Sheets

Code.gs

// AUTO GENERATE SIMPLE UNIQUE ID'S FOR NON-EMPTY ROWS
//
// Author: Carlos Perez, clayperez@gmail.com
//
// Purpose: This Google Sheets script fires when any cell is edited and
// inserts a random uuid (generated via Google Sheets's provided getUuid utility)
// into the specified ID_COLUMN. For instance if the first column in the
// sheet specified by SHEETNAME is the column where you would like the
// UID injected, then ID_COLUMN should be 1.
//
// SETTINGS
// SHEETNAME = Name of spreadsheet to monitor
// 
// 
// REFERENCES:
// https://developers.google.com/apps-script/guides/triggers/events
// https://www.fiznool.com/blog/2014/11/16/short-id-generation-in-javascript/

var SHEETNAME = "Shifts";
var ID_COLUMN = 1;

function onEdit(evt) {
  var range = evt.range;
  var sheet = range.getSheet();
  if(sheet.getSheetName() !== SHEETNAME) return;

  // getValues()
  // as cells: [[A1,B1,C1],[A2,B2,C2],[A3,B3,C3],[A4,B4,C4],[...]]
  // as locals: [[11,21,31],[12,22,32],[13,23,33],[14,24,34],[...]]
  var rangeValues = range.getValues();

  // Loop over each row of the range and check for data being entered.
  // We don't want to commit a UID value to the ID column if the data
  // in adjacent columns was just deleted. We only want a UID for rows
  // with data in them.
  rangeValues.forEach(function(row,index,arr){
    var conc = row.join("").length; // Where we check for data in the row
    if(conc > 0) { // The current row edited is NOT empty. Proceed.
      var idRange = sheet.getRange( range.getRow() + index, ID_COLUMN ); // This is a 1-dimensional range that contains the ID cell we want to populate
      var idCell = idRange.getCell( 1, 1 ); // This drills down into that single-dimensional range and picks out the cell (yeah, seems redundant but... Google)
      var idValue = idCell.getValue(); // This is the actual value of that ID cell. If there's already a UID in there, we DO NOT want to change it.
      if (idValue == "") {
        idCell.setValue( Utilities.getUuid() ); // Ok, everything above checks out. Let's give this row a UID
      }
    }
  });
  
}