Help: The getElementById returns 'undefined'. Followed the instructor's verbatim and still received undefined value. Please see the code below.

//first, define questions and answers in an Array var questions = [ ['what is 1 + 1?', 2], ['what is 2 + 2?', 4], ['what is 3 + 3?', 6], ]

//define variables to help make code readable var correctAnswer = 0; var question; var answer; var response; var html; var correct = []; var wrong = [];

function print(message) { var outputDiv = document.getElementById('output'); outputDiv.innerHTML = message; }

function buildList (arr) { var myList1 = '<ol>';
for (var i = 0; i < arr.length; i += 1) { myList1 += '<li>' + arr[i] + '</li>'; } myList1 += '</ol>'; return myList1; }

//iterate through questions in variable 'questions'
for ( var i = 0; i < questions.length; i+= 1) { //set question question = questions[i][0]; //set answer to above question answer = questions[i][1]; //display question to user response = parseInt(prompt(question)); //validate answers and increment correctAnswer if (response === answer) { correctAnswer += 1; correct.push( question ); } else { wrong.push( question ); } } html += "You got " + correctAnswer + " question(s) right!"; html += '<h2>You got these questions right'; html += buildList(correct); html += '<h2>You got these questions wrong'; html += buildList(wrong); print(html);