Google App Script to geocode a list of addresses in a Spreadsheet

Code.gs

function myFunction() {
  var sheet = SpreadsheetApp.getActiveSheet();
  
  var range = sheet.getDataRange();
  var cells = range.getValues();
  
  var latitudes = [];
  var longitudes = [];
  
  for (var i = 0; i < cells.length; i++) {
    var address = cells[i][0];
    var geocoder = Maps.newGeocoder().geocode(address);
    var res = geocoder.results[0];
  
    latitudes.push([res.geometry.location.lat]);
    longitudes.push([res.geometry.location.lng]);
  }
  
  sheet.getRange('B1').offset(0, 0, latitudes.length).setValues(latitudes)
  sheet.getRange('C1').offset(0, 0, latitudes.length).setValues(longitudes);
}