Why don't the right and wrong lists print?

var quizList = [
  ["What the color is made from mixing red and yellow?", "orange"],
  ["What the color is made from mixing blue and red?", "purple"],
  ["What the color is made from mixing yellow and blue?", "green"]
];

var correctAnswers = 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 listHTML = "<ol>";
  for (var i = 0; i < arr.legnth; i++ ) {
    listHTML += "<li>" + arr[i] + "</li>";
  }
  listHTML += "</ol>";
  return listHTML;
}


for ( var i = 0; i < quizList.length; i++) {
  question = quizList[i][0];
  answer = quizList[i][1];
  response = prompt(question).toLowerCase();
  if ( response === answer ){
    correctAnswers += 1;
    correct.push(question);
  } else {
    wrong.push(question);
  }
}

html = "You get " + correctAnswers + " question(s) right.";
html += "<h2>You got these questions correct:</h2>";
html += buildList(correct);
html += "<h2>You got these questions wrong:</h2>";
html += buildList(wrong);
print(html);