Starting a Sidebar in Google Apps Script

Starting a sidebar takes one HTML file, and a script file containing just two Apps Script functions.

[caption id=“attachment_715” align=“alignnone” width=“1024”]Starting an Apps Script Sidebar Starting an Apps Script Sidebar[/caption]

The Apps Script functions:

function onOpen() {
  SpreadsheetApp.getUi()
    .createMenu("Example Menu")
    .addItem("Menu Item", "exampleSidebar")
    .addToUi();
}   
  
function exampleSidebar() {
  let sidebar =  HtmlService.createHtmlOutputFromFile("ExampleHTML");
  SpreadsheetApp.getUi().showSidebar(sidebar.setTitle("The Sidebar Title"));
}

The HTML file (exampleHTML.html):

<!DOCTYPE html>
<html>
  <head>
    <base target="_top">
  </head>
  <body>
 
  </body>
</html>

Reference:

Google Developer Guide