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JavaScript JavaScript Loops, Arrays and Objects Tracking Multiple Items with Arrays Build a Quiz Challenge, Part 1

Thomas Marren
Thomas Marren
3,626 Points
Posted by Thomas Marren
Thomas Marren
3,626 Points

Only one question shows up on my list

When I run this code the only question that shows up on the webpage is "What is the capital of the USA?" If I answer it correct it goes in the correct array if I answer it incorrect it goes in the incorrect array and the other array says undefined on the webpage.

What am I doing wrong?

function print(message) {
  document.write(message);
}

var questions = [
  ['What is the capital of NY?' , 'Albany'] ,
  ['What is the capital of PA?' , 'Harrisburg'] ,
  ['What is the capital of the USA?' , 'Washington DC']
];

var score = 0;
var correct = [ ];
var incorrect = [ ];


//ask the questions

for (var i = 0; i < questions.length; i++) {
var userAnswer = prompt(questions[i][0]);
   if ( userAnswer === questions[i][1] ) {
   correct.push(questions[i][0]);
   score += 1;
  } else {
   incorrect.push(questions[i][0]);
  }
}


//print the total number of questions correct

print('You got ' + score + ' question(s) right');


//create a list of each array for correct and incorrect

for (var i = 0; i < correct.length; i++){
  var correctList = '<ol>';
  correctList += '<li>' + correct[i] + '</li>';
  correctList += '</ol>';
}

for (var i = 0; i < incorrect.length; i++){
  var incorrectList = '<ol>';
  incorrectList += '<li>' + incorrect[i] + '</li>';
  incorrectList += '</ol>';
}

print("You got these questions right " + correctList);
print("You got these questions wrong " + incorrectList);

1 Answer

Shawn Boyd
Shawn Boyd
14,345 Points
Shawn Boyd
Shawn Boyd
14,345 Points

In your loops for printing out the list of answered and unanswered questions you are initializing the variable holding the ordered list with each iteration of the loop. Meaning that only the last iteration, if there is one, will be held within the variable. If one of the for loops never runs because all of the answers were correct or all were incorrect then that variable (correctList or incorrectList) will never be initialized and result in an undefined value when you get to the print command.

To fix this, initialize the variable that you'll use to hold the list items outside of the for loop, including opening and closing ol tags. Inside the loop you should only be adding list items, as appropriate. Something like this...

...
//start ordered list
var correctList = '<ol>';

//add questions answered correctly, if any
for (var i = 0; i < correct.length; i++){
  correctList += '<li>' + correct[i] + '</li>';
  }
//close ordered list
correctList += '</ol>';

//start ordered list
var incorrectList = '<ol>';

//add questions answered incorrectly, if any
for (var i = 0; i < incorrect.length; i++){
  incorrectList += '<li>' + incorrect[i] + '</li>';
  }
//close ordered list
incorrectList += '</ol>';

//print list of correct and incorrect
print("You got these questions right " + correctList);
print("You got these questions wrong " + incorrectList);
Thomas Marren
Thomas Marren
3,626 Points
Thomas Marren
Thomas Marren
3,626 Points

Thanks Shawn! This was driving me crazy. I wound up scraping the whole thing and creating a function. But this definitely helped me understand to be careful with what goes into the for loops.