Client Side Code creation and Apps Script to get Sheet data to web app Client Side JavaScript

function doGet() {
  const template = HtmlService.createTemplateFromFile('Index');
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  const data = sheet.getDataRange().getValues();
  template.data = JSON.stringify(data);
  
  return template.evaluate();
}

function setup() {
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  const sheet = ss.getActiveSheet();
  sheet.getRange("A1").setValue("Name");
  sheet.getRange("A2").setValue("Alice");
  sheet.getRange("A3").setValue("Bob");
  // Add more initial data as needed
}