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

Posted by Michelle Tan
Michelle Tan
2,345 Points

Code help please? (35 lines)

Hello,

Would appreciate some help on this:

Final result was this: "You got 1 correct answers. You got these questions right:

undefined What is 90 - 45? You got these questions wrong: undefined What is 2 + 2? What is 2 * 2?"

My code is 

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

var questions = [
  ['What is 2 + 2?' , '4'],
  ['What is 2 * 2?' , '4'],
  ['What is 90 - 45?' , '45'],
    ];

var correct = [];
var wrong = [];
var questionData;
var questionMessage;
var questionAnswer;
var questionResponse;
var correctList;
var wrongList;

  for ( var i = 0 ; i < questions.length ; i += 1 ) {
   questionData = questions[i];
   questionAnswer = questionData[1];
   questionResponse = prompt(questionData[0]);
   if (questionResponse === questionAnswer) {
   correct.push(questionData[0]);
   correctList += "<li>" + questionData[0] + "</li>";
  } else {
   wrong.push(questionData[0]);
   wrongList += "<li>" + questionData[0] + "</li>";
  }
}

var html = "<h2> You got "  + correct.length + " correct answer(s).</h2> <p> You got these questions right: </p><ol>" + correctList + "</ol><h2> You got these questions wrong:</h2><ol>" + wrongList + "</ol>"

print(html);

Comments much appreciated :)

2 Answers

akak
akak
29,446 Points
akak
akak
29,446 Points 
var correctList;
console.log(correctList) // prints out 'undefined'

Variable declared like that starts with "undefined" value. If you overwrite it later with data it's not a big deal. But here you're just adding data to it by += so your adding to undefined. That's why you have undefined at the beginning of the sentence. Initialize it with an empty string like var correctList = "" instead.

Michelle Tan
Michelle Tan
2,345 Points

Thank you for your help :)

Erik Nuber
Erik Nuber
20,629 Points
Erik Nuber
Erik Nuber
20,629 Points

You are very close. You need to define your correctList and wrongList with no content

correctList = "";
wrongList = "";

This is why you are getting an undefined when you just add to the list itself.

You are saying += and when correctList is nothing to begin with it is considered undefined. So your correctList will hold

undefined + <li></li> + <li></li>

if two answers are correct.

Michelle Tan
Michelle Tan
2,345 Points

Thank you for the answer! :)