Add two numbers present on sheet on User Alert using Google Apps Script

function addtwonumbersonsheet() {
 
var sh1=SpreadsheetApp.getActiveSpreadsheet();
var sheet1=sh1.getSheetByName("GAS_Sheet");
var num1=sheet1.getRange(2,1).getValue();
var num2=sheet1.getRange(2,2).getValue();  
var sh=SpreadsheetApp.getUi();
var response=sh.alert("Do you want to add the two number?",sh.ButtonSet.YES_NO);
if (response == sh.Button.YES)
{
  sheet1.getRange(2,3).setValue(num1+num2);
 
}

}

Taking input and Switch Case using Google Apps Script

//Declaring variables
var ui = SpreadsheetApp.getUi();
// Get the value from the user
var get_text= ui.prompt("Enter any number from 1 to 7").getResponseText();
//Convert the data type to integer
var get_num=parseInt(get_text);
//Comparing the entered number with days in a week
switch(get_num)
 {
   
   case 1:
        ui.alert("Today is sunday");
        break;   
   case 2:
        ui.alert("Today is monday");
        break;
   case 3:
        ui.alert("Today is tuesday");
        break;
   case 4:
        ui.alert("Today is Wednesday")
        break;
   case 5:
       ui.alert("Today is Thursday");
        break;
   case 6:
        ui.alert("Today is Friday");
        break;
   case 7:
        ui.alert("Today is Saturday");
        break;
   default:
         ui.alert("Entered number is not fall between 1 to 7")
 }






 

Toast Pop Up Using Google Apps Script

function greeting()
{
  SpreadsheetApp.getActiveSpreadsheet().toast("toast tester", "greeting", (number of seconds ,-1 for permanent)
 
 
 
}

Hello world using google apps script

function hello_world() {
  var my_message="hello world";
  SpreadsheetApp.getUi().alert(my_message);
}