Apps Script Basics - if, prompt, menu, & onOpen trigger (2)

6If-menu-prompt-onOpen

//Set background to red if attendance is less than 80%
function example1() {
  var ss = SpreadsheetApp.getActiveSheet();
  var attendance = ss.getRange("B3").getValue();
  
  if (attendance < 0.8) {
    ss.getRange("B3").setBackground("red");
  }
}

//Set background to red if attendance is less than 80%
//Otherwise set it to green
function example2() {
  var ss = SpreadsheetApp.getActiveSheet();
  var attendance = ss.getRange("B3").getValue();
  
  if (attendance < 0.8) {
    ss.getRange("B3").setBackground("red");
  }
  
  else {
    ss.getRange("B3").setBackground("green"); 
  }
}

//Set background to red if attendance is less than 70%
//Set background to yellow if attendance is 70-80%
//Set background to green if attendance is 80% or more
function example3() {
  var ss = SpreadsheetApp.getActiveSheet();
  var attendance = ss.getRange("B3").getValue();
  
  if (attendance < 0.7) {
    ss.getRange("B3").setBackground("red");
  }

  else if (attendance < 0.8) {
    ss.getRange("B3").setBackground("yellow");
  }
  
  else {
    ss.getRange("B3").setBackground("green"); 
  }
}

//Set background of name to red if
//attendance is less than 80% OR exam is less than 70%
function example4() {
  var ss = SpreadsheetApp.getActiveSheet();
  var attendance = ss.getRange("E3").getValue();
  var exam = ss.getRange("F3").getValue();
  
  if (attendance < 0.8 || exam < 0.7) {
    ss.getRange("D3").setBackground("red");
  }
  
  else {
    ss.getRange("D3").setBackground("green"); 
  }
}

//Set background of name to green if
//attendance is 80% or more AND exam is 70% or more
function example5() {
  var ss = SpreadsheetApp.getActiveSheet();
  var attendance = ss.getRange("E3").getValue();
  var exam = ss.getRange("F3").getValue();
  
  if (attendance >= 0.8 && exam >= 0.7) {
    ss.getRange("D3").setBackground("green");
  }
  
  else {
    ss.getRange("D3").setBackground("red"); 
  }
}

//Open sheet from name in cell B4 and paste student's data
function example6() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet1 = ss.getSheetByName('Sheet1');
  var name = sheet1.getRange("B5").getValue();
  
  if(name === "John") {
     var figures = sheet1.getRange("A7:E9").getValues();
  }
  
  else if(name === "Ringo") {
    var figures = sheet1.getRange("A10:E12").getValues();
  }
  
  else if(name === "Paul") {
    var figures = sheet1.getRange("A13:E15").getValues();
  }
  
  else if(name === "George") {
    var figures = sheet1.getRange("A16:E18").getValues();
  }

  var studentSheet = ss.getSheetByName(name).activate();
  studentSheet.getRange("A1:E3").setValues(figures);
}

//Return back to Sheet1
function example6b() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet1 = ss.getSheetByName('Sheet1').activate();
}

//Ask which sheet user wants to open and then open it
function example7() {
 var ss = SpreadsheetApp.getActiveSpreadsheet();
 var ui = SpreadsheetApp.getUi();
 var response = ui.prompt('Enter name:');

 if (response.getSelectedButton() === ui.Button.OK) {
   var name = response.getResponseText();
   ss.getSheetByName(name).activate();
 } else {
 }
}

//Using ternary operator-If less than 80% set background red, otherwise green
function example8() {
  var ss = SpreadsheetApp.getActiveSheet();
  var cellB3 = ss.getRange("B3");
  var attendance = cellB3.getValue(); 
  (attendance < 0.8) ? cellB3.setBackground("red"):cellB3.setBackground("green");
}

//Set background colour for all students' attendance figures
function example9() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet1 = ss.getSheetByName('Sheet1');
  var attendanceFigures = sheet1.getRange("I3:I6").getValues();

  for (i=0;i<attendanceFigures.length;i++){

  var r = i+3;
    
  if (attendanceFigures[i] < 0.7) {
    sheet1.getRange(r,9).setBackground("red");
  }  
    
  else if (attendanceFigures[i] < 0.8) {
    sheet1.getRange(r,9).setBackground("yellow");
  }

  else {
    sheet1.getRange(r,9).setBackground("green"); 
  }
  }
}

Hi,I'm first time user to google script and have tried example7 which is getting me error "cannot call SpreadsheetApp.getUi() from this context"
here is my code
function prompt()
{
var ss =SpreadsheetApp.openById('XXXXXX');
var sh = ss.getSheetByName('Sheet');
var spreadsheet=ss.getActiveSheet();
Logger.log(sh)
var ui=SpreadsheetApp.getUi();
var response=ui.prompt('Enter name:');
}