https://www.pbainbridge.co.uk/2018/12/push-items-into-empty-array.html

Push items into empty array.gs

function pushToArray() {
  
  // create an empty array
  var students = []
  Logger.log('students array starts empty: ' + students);
  
  // array with items to be pushed
  var age = [7,8,9];
  
  // loop through each item and push into empy array
  for (i=0;i<age.length;i++) {
    students.push(age[i]);
  }
  
  // log output of new array
  Logger.log('students array now contains: ' + students);
  
}