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JavaScript JavaScript Loops, Arrays and Objects Tracking Multiple Items with Arrays Build a Quiz Challenge, Part 2 Solution


how does arr have a length? It seems to me that this is not an array. If it is an array, what data is in it and how did it get filled with data?

2 Answers

Are you referring to this section of the code?

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

If so, the contents of arr (and hence the length) are being created at the end of the file, when you call buildList:

html += '<h2>You got these right: </h2>';
html += buildList(correct);

buildList is using the 'correct' array as its argument, which starts out empty:

var correct = [];

and is populated by the for loop:

for (var i = 0; i < questions.length; i += 1) {
  question = questions[i][0];
  answer = questions[i][1];
  response = prompt(question);
  response = parseInt(response);
  if (response === answer) {
    correctAnswers += 1;

Yes, exactly, Thank You.