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

Jacob Jozefowicz
Jacob Jozefowicz
3,284 Points

TypeError: questionsAndAnswers[i] is undefined

I keep getting that error in the console.

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

function list(x) {
  var listed = x.join(" - ");
  return listed;
}
var correctAnswers = 0;

var questionsAndAnswers = [
  ["What is after 2?", "3"],
  ["Capital of Ireland?", "dublin"],
  ["Write 3 in word form", "three"]
];


for(var i = 0; i <= 3; i++)
{

  var rightAnswer = questionsAndAnswers[i][1];
  var userAnswer = prompt(questionsAndAnswers[i][0]);
  questionsAndAnswers[i].push(userAnswer);
  if(rightAnswer == userAnswer)
  {
    questionsAndAnswers[i].push("Correct");
    correctAnswers++;
  }
  else
  {
   questionsAndAnswers[i].push("Wrong"); 
  }
}


for( var i = 0; i <= 3; i++)
{
var stats = list(questionsAndAnswers[i]);
print(stats);
}
print(correctAnswers);
            ```

1 Answer

Nicholas Olsen
seal-mask
.a{fill-rule:evenodd;}techdegree
Nicholas Olsen
Front End Web Development Techdegree Student 19,342 Points

Both of your for loops count from 0 to 3, they should count from 0 to 2.

Arrays start a 0, so if you have 3 elements in an array, you only count to 2 because "0, 1, 2" is three numbers total. So right now, your loop goes through 3 times as it should, but then on the 4th time it looks for questionsAndAnswers[3], which is undefined.

The solve this, just replace " i < = 3 " with " i < 3 " or " i < = 2 " in both for loops.

Most of the time people write "i < 3"

I would also suggest that you use i < questionsAndAnswers.length to make your program a little more dynamic.

Currently you have 2 places that you have to remember to go back and change a number if you add or remove questions from your array.

Jacob Jozefowicz
Jacob Jozefowicz
3,284 Points

Damn it, I thought it might be a careless mistake like that. Thank you!