如果sessionStorage中没有可用的数据，我会尽量避免调用服务器端函数getSuppliersForPoFromSS(orderPo, origin)，但我不确定是否得到了正确的结构：

**/
 * Gets determined supplier from Spreadsheet and builds a select input with options.
 * @param {Object} selecObject
 * @param {String} origin specifying where this is going to be obtained from
 */
function loadSuppliersForPoFromSS(selectObject, origin) {
  orderPo = selectObject.value;
  document.getElementById('selectSupplier').innerHTML = '';
   
  //My shot at it, trying to a 2D array. e.g.: [["Item1", "Item2"]]
  let ar = JSON.parse(sessionStorage.getItem(orderPo));
 
   
  if(!ar){   
  google.script.run.withSuccessHandler(function(ar) {
    let select = document.getElementById('selectSupplier');
    let options = select.getElementsByTagName('option');
    for (let i = options.length; i--;) {
      select.removeChild(options[i]);
    }
    let option = document.createElement("option");
    option.value = "";
    option.text = "";
    select.appendChild(option);
    ar.forEach(function(item, index) {
      let option = document.createElement("option");
      option.value = item.toLowerCase();
      option.text = item;
      select.appendChild(option)
    });
  }).getSuppliersForPoFromSS(orderPo, origin);
 } else {
  //Do I rewrit the part that builds the options with data from sessionStorage?
}