GAS WEBアプリにて既存のGoogle Spread Sheetからデータを読み出す

実際のところ

Spread Sheetに

1,A,あ
2,B,い
3,C,う

上記ファイルのidが'1234567890abcdefghijklmnopqrstuvwxyz'であるとき、
code.gsは

function doGet() {
  var template = HtmlService.createTemplateFromFile('hello.html');
  return template.evaluate().setSandboxMode(HtmlService.SandboxMode.IFRAME);
}

function getData() {
  var fileid = '1234567890abcdefghijklmnopqrstuvwxyz';
  return SpreadsheetApp
      .openById(fileid)
      .getActiveSheet()
      .getDataRange()
      .getValues();
}

hello.html

<!DOCTYPE html>
<html>
  <head>
    <base target="_top">
  </head>
  <body>
  
  <p>List of things:</p>
    <ul id="data">
      <li>Loading...</li>
  </ul> 
  </body>
</html>

<script
src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">
</script>
<script>
// The code in this function runs when the page is loaded.
$(function() {
  google.script.run.withSuccessHandler(showThings)
      .getData();
});

function showThings(things) {
  var list = $('#data');
  list.empty();
  for (var i = 0; i < things.length; i++) {
    list.append('<li>' + things[i][i] + '</li>');
  }
}
</script>